Prevent Nullptr segfault in TurboModule init path

Summary:
During the TurboModule init path, the TurboModuleManager asks the application to create the TurboModule object, given its class.

If the application is unable to create the TurboModule object, what should we do?
0. **What we do now:** Continue executing TurboModule init path.
1. Silently return nil early.
2. Silently return nil early, and RCTLogError.

If we Continue executing the TurobModule init path, we'll run into a segfault, because we'll call objc_setAssociatedObject(nil, ...).

This diff prevents that segfault, by doing a silent return of nil.

Changelog: [iOS][Fixed] - Prevent Nullptr segfault in TurboModule init path

Reviewed By: fkgozali

Differential Revision: D35942323

fbshipit-source-id: 7755800379c4bc733502314f3af3f401e9b04872

ReactCommon/react/nativemodule/core/platform/ios/RCTTurboModuleManager.mm

@@ -521,6 +521,19 @@ static Class getFallbackClassFromName(const char *name)
       std::lock_guard<std::mutex> delegateGuard(_turboModuleManagerDelegateMutex);
       module = [_delegate getModuleInstanceFromClass:moduleClass];
     }
+
+    /**
+     * If the application is unable to create the TurboModule object from its class:
+     * abort TurboModule creation, and early return nil.
+     */
+    if (!module) {
+      RCTLogWarn(
+          @"TurboModuleManager delegate %@ returned nil TurboModule object for module with name=\"%s\" and class=%@",
+          NSStringFromClass([_delegate class]),
+          moduleName,
+          NSStringFromClass(moduleClass));
+      return nil;
+    }
   } else {
     module = [moduleClass new];
   }