diff --git a/include/Controller.php b/include/Controller.php
index 8b335a11..043c0b55 100644
--- a/include/Controller.php
+++ b/include/Controller.php
@@ -118,6 +118,7 @@ class Controller
     {
         /* Properly encode all ampersands as "&". */
         $string = preg_replace('/&(?!([a-z]+|(#\d+));)/i', '&', $string);
+        assert($string !== null);
         /* Replace weird characters that appears in some of the data. */
         return $string;
     }
@@ -158,7 +159,9 @@ class Controller
     public function releaseSmartyModifier(string $string): string
     {
         $string = preg_replace("/\{[$]?release\}/", RELEASE, $string);
+        assert($string !== null);
         $string = preg_replace("/\{[$]?release_tools\}/", RELEASE_TOOLS, $string);
+        assert($string !== null);
         return $string;
     }
 
diff --git a/include/LocalizationUtils.php b/include/LocalizationUtils.php
index 632c11c3..45e46a06 100644
--- a/include/LocalizationUtils.php
+++ b/include/LocalizationUtils.php
@@ -90,7 +90,9 @@ class LocalizationUtils
                     $content = preg_replace_callback(
                         "/(?<=\(http)(.*?)(?=\))/u",
                         function (array $matches): string {
-                            return preg_replace("/\x{202f}/u", "", $matches[1]);
+                            $ret = preg_replace("/\x{202f}/u", "", $matches[1]);
+                            assert($ret !== null);
+                            return $ret;
                         },
                         $content
                     );
diff --git a/include/Models/DownloadsModel.php b/include/Models/DownloadsModel.php
index 5ae2b420..cd33c485 100644
--- a/include/Models/DownloadsModel.php
+++ b/include/Models/DownloadsModel.php
@@ -53,7 +53,7 @@ class DownloadsModel extends BasicModel
                     $sections[$category] = new DownloadsSection([
                         'anchor' => $category,
                         'title' => $sectionsData[$category]['title'],
-                        'notes' => $sectionsData[$category]['notes'] ?? null
+                        'notes' => $sectionsData[$category]['notes'] ?? ''
                     ]);
                 }
 
@@ -62,7 +62,7 @@ class DownloadsModel extends BasicModel
                     $sections[$category]->addSubsection(new DownloadsSection([
                         'anchor' => $subCategory,
                         'title' => $sectionsData[$subCategory]['title'],
-                        'notes' => $sectionsData[$subCategory]['notes'] ?? null
+                        'notes' => $sectionsData[$subCategory]['notes'] ?? ''
                     ]));
                 }
 
@@ -115,6 +115,8 @@ class DownloadsModel extends BasicModel
         $osParser = new OsParser();
         $osParser->setUserAgent($_SERVER['HTTP_USER_AGENT']);
         $os = $osParser->parse();
+        // Should never happen: the DeviceDetector signature seems wrong
+        assert($os !== null);
 
         $downloads = DownloadQuery::create()
             ->setIgnoreCase(true)
diff --git a/include/Models/GameDownloadsModel.php b/include/Models/GameDownloadsModel.php
index 66fb72f7..ba857efb 100644
--- a/include/Models/GameDownloadsModel.php
+++ b/include/Models/GameDownloadsModel.php
@@ -29,8 +29,8 @@ class GameDownloadsModel extends BasicModel
             foreach ($categories as $category) {
                 $sections[$category] = new DownloadsSection([
                         'anchor' => $category,
-                        'title' => $sectionsData[$category]['title'] ?? null,
-                        'notes' => $sectionsData[$category]['notes'] ?? null
+                        'title' => $sectionsData[$category]['title'] ?? '',
+                        'notes' => $sectionsData[$category]['notes'] ?? ''
                     ]);
             }
 
@@ -48,7 +48,7 @@ class GameDownloadsModel extends BasicModel
                     $sections[$category]->addSubsection(new DownloadsSection([
                         'anchor' => $gameId,
                         'title' => $gameName,
-                        'notes' => $sectionsData[$gameId]['notes'] ?? null
+                        'notes' => $sectionsData[$gameId]['notes'] ?? ''
                     ]));
                 }
 
diff --git a/include/Objects/DownloadsSection.php b/include/Objects/DownloadsSection.php
index c9ffb764..dc295ce4 100644
--- a/include/Objects/DownloadsSection.php
+++ b/include/Objects/DownloadsSection.php
@@ -48,7 +48,7 @@ class DownloadsSection extends BasicSection
                     }
 
                     // Return 0 if equal, -1 if $a->getVersion() is larger, 1 if $b->getVersion() is larger
-                    $versionSortResult = -version_compare($a->getVersion(), $b->getVersion());
+                    $versionSortResult = -version_compare($a->getVersion() ?? '', $b->getVersion() ?? '');
                     if ($versionSortResult == 0) {
                         // Return 0 if equal, -1 if $a->getAutoId() is smaller, 1 if $b->getAutoId() is smaller
                         return $a->getAutoId() <=> $b->getAutoId();
diff --git a/include/Objects/News.php b/include/Objects/News.php
index 65b28205..ccd68785 100644
--- a/include/Objects/News.php
+++ b/include/Objects/News.php
@@ -66,6 +66,7 @@ class News
             return substr_replace($full, $lurl, $urlOffset, strlen($url));
         }, $body, flags: PREG_OFFSET_CAPTURE);
 
+        assert($body !== null);
         return $body;
     }
 
diff --git a/include/OrmObjects/Compatibility.php b/include/OrmObjects/Compatibility.php
index 4cb991e7..9f670f06 100644
--- a/include/OrmObjects/Compatibility.php
+++ b/include/OrmObjects/Compatibility.php
@@ -56,7 +56,7 @@ class Compatibility extends BaseCompatibility
 
         if ($this->notes) {
             $notes .= "### Additional Notes\n";
-            $notes .= str_replace("- ", "\n- ", parent::getNotes()) . "\n";
+            $notes .= str_replace("- ", "\n- ", parent::getNotes() ?? '') . "\n";
         }
 
         $links = [];
diff --git a/include/Pages/CompatibilityPage.php b/include/Pages/CompatibilityPage.php
index d5de41ed..dc196684 100644
--- a/include/Pages/CompatibilityPage.php
+++ b/include/Pages/CompatibilityPage.php
@@ -73,7 +73,7 @@ class CompatibilityPage extends Controller
             ->find()->toArray();
 
         /* Default to DEV */
-        if (!in_array($version, $versions)) {
+        if (empty($version) || !in_array($version, $versions)) {
             $version = 'DEV';
         }
 
@@ -99,13 +99,13 @@ class CompatibilityPage extends Controller
 
         $this->renderPage(
             array(
-                'title' => preg_replace('/{version}/', $version, $this->getConfigVars('compatibilityTitle')),
+                'title' => preg_replace('/{version}/', $version, $this->getConfigVars('compatibilityTitle') ?? ''),
                 'subtitle' => $game->getGame()->getName(),
                 'description' => $this->supportLevelDescriptions[$game->getSupport()],
                 'content_title' => preg_replace(
                     '/{version}/',
                     $version,
-                    $this->getConfigVars('compatibilityContentTitle')
+                    $this->getConfigVars('compatibilityContentTitle') ?? ''
                 ),
                 'version' => $version,
                 'game' => $game,
@@ -130,12 +130,12 @@ class CompatibilityPage extends Controller
 
         $this->renderPage(
             [
-                'title' => preg_replace('/{version}/', $version, $this->getConfigVars('compatibilityTitle')),
+                'title' => preg_replace('/{version}/', $version, $this->getConfigVars('compatibilityTitle') ?? ''),
                 'description' => $this->getConfigVars('compatibilityIntro'),
                 'content_title' => preg_replace(
                     '/{version}/',
                     $version,
-                    $this->getConfigVars('compatibilityContentTitle')
+                    $this->getConfigVars('compatibilityContentTitle') ?? ''
                 ),
                 'version' => $version,
                 'compat_data' => $compat_data,
diff --git a/include/Pages/DownloadsPage.php b/include/Pages/DownloadsPage.php
index 6c864a4c..a5ee54e3 100644
--- a/include/Pages/DownloadsPage.php
+++ b/include/Pages/DownloadsPage.php
@@ -23,7 +23,7 @@ class DownloadsPage extends Controller
         $this->renderPage(
             array(
                 'title' => $this->getConfigVars('downloadsTitle'),
-                'description' => \strip_tags($this->getConfigVars('downloadsContentP1')),
+                'description' => \strip_tags($this->getConfigVars('downloadsContentP1') ?? ''),
                 'content_title' => $this->getConfigVars('downloadsContentTitle'),
                 'downloads' => $downloads,
                 'recommendedDownload' => $recommendedDownload
diff --git a/include/Pages/GamesPage.php b/include/Pages/GamesPage.php
index ebf4aed3..88d546ed 100644
--- a/include/Pages/GamesPage.php
+++ b/include/Pages/GamesPage.php
@@ -23,7 +23,7 @@ class GamesPage extends Controller
         $this->renderPage(
             array(
                 'title' => $this->getConfigVars('gamesTitle'),
-                'description' => strip_tags($this->getConfigVars('gamesContentP1')),
+                'description' => strip_tags($this->getConfigVars('gamesContentP1') ?? ''),
                 'content_title' => $this->getConfigVars('gamesContentTitle'),
                 'downloads' => $downloads,
             )
diff --git a/public_html/index.php b/public_html/index.php
index 1a4ff68b..82097ed0 100644
--- a/public_html/index.php
+++ b/public_html/index.php
@@ -153,6 +153,7 @@ if ($match === false) {
 }
 
 if ($match['target'] === '\ScummVM\Pages\SimplePage' || $match['target'] === '\ScummVM\Pages\StaticPage') {
+    assert($match['name'] !== null);
     $page = new $match['target']($match['name']);
 } elseif (strpos($match['target'], "http") === 0) {
     header("Location: {$match['target']}");