Check for RCTSettingsManager in Settings.ios

Libraries/Settings/Settings.ios.js

@@ -19,7 +19,7 @@ var invariant = require('invariant');
 var subscriptions: Array<{keys: Array<string>; callback: ?Function}> = [];
 
 var Settings = {
-  _settings: RCTSettingsManager.settings,
+  _settings: RCTSettingsManager && RCTSettingsManager.settings,
 
   get(key: string): mixed {
     return this._settings[key];