Ulangi aborts on launch on iPhone 4S

[stevehartwell]

The app is registered in the App Store to be compatible with iOS 9.0, but after installing it on an iPhone 4S running iOS 9.3, it quits immediately after launch with the following log messages:

May  8 22:34:51 iFourS Ulangi[648] <Warning>: Unknown class _TtC6Ulangi26LaunchScreenViewController in Interface Builder file.
May  8 22:34:51 iFourS Ulangi[648] <Notice>: 6.27.1 - [Firebase/Messaging][I-FCM001000] FIRMessaging Remote Notifications proxy enabled, will swizzle remote notification receiver handlers. If you'd prefer to manually integrate Firebase Messaging, add "FirebaseAppDelegateProxyEnabled" to your Info.plist, and set it to NO. Follow the instructions at:
	https://firebase.google.com/docs/cloud-messaging/ios/client#method_swizzling_in_firebase_messaging
	to ensure proper integration.
May  8 22:34:53 iFourS kernel[0] <Notice>: 004507.040803 wlan0.A[196] updateRxDataRSSI@2591:Rx Data Rssi 18 dBm is out of range?
May  8 22:34:53 iFourS securityd[86] <Error>:  securityd_xpc_dictionary_handler cloudd[402] copy_matching Error Domain=NSOSStatusErrorDomain Code=-50 "query missing class name" UserInfo={NSDescription=query missing class name}
May  8 22:34:53 iFourS Ulangi[648] <Warning>: Received memory warning.
May  8 22:34:53 iFourS SpringBoard[235] <Warning>: Received memory warning.
May  8 22:34:55 iFourS Ulangi[648] <Notice>: 6.27.1 - [Firebase/Analytics][I-ACS031025] Analytics screen reporting is enabled. Call +[FIRAnalytics setScreenName:setScreenClass:] to set the screen name or override the default screen class name. To disable screen reporting, set the flag FirebaseScreenReportingEnabled to NO (boolean) in the Info.plist
May  8 22:34:55 iFourS Ulangi[648] <Notice>: 6.27.1 - [Firebase/Analytics][I-ACS023007] Analytics v.60602000 started
May  8 22:34:55 iFourS Ulangi[648] <Notice>: 6.27.1 - [Firebase/Analytics][I-ACS023008] To enable debug logging set the following application argument: -FIRAnalyticsDebugEnabled (see http://goo.gl/RfcP7r)
May  8 22:34:55 iFourS Ulangi[648] <Warning>: 6.27.1 - [Firebase/Analytics][I-ACS800023] No pending snapshot to activate. SDK name: app_measurement
May  8 22:34:55 iFourS Ulangi[648] <Error>: *** Terminating app due to uncaught exception 'RCTFatalException: Unhandled JS Exception: Error: [mobx] MobX 5+ requires Proxy and Symbol objects. If your environment doesn't support Symbol or Proxy objects, please downgrade to MobX 4. For React Native Android, consider upgrading JSCore.', reason: 'Unhandled JS Exception: Error: [mobx] MobX 5+ requires Proxy and Symbol objects. If your environment doesn't support Symbol or Proxy objects, please downgrade to MobX 4. For R..., stack:
	<unknown>@467:51577
	v@2:1474
	d@2:946
	o@2:414
	<unknown>@466:491
	v@2:1474
	d@2:946
	o@2:414
	<unknown>@465:98
	v@2:1474
	d@2:946
	o@2:414
	<unknown>@7:152
	v@2:1474
	d@2:946
	o@2:414
	<unknown>@6:35
	v@2:1474
	d@2:876
	o@2:414
	global code@2838:4
	'
	*** First throw call stack:
	(0x239cf91b 0x2316ae17 0x28af73 0x2f8b25 0x239d44c4 0x238fa87d 0x238fe2f7 0x2be81f 0x2c093d 0x2c05a7 0x2353d823 0x2354a423 0x23549a61 0x2354c5e9 0x2354bfcd 0x23701b29 0x23701718)
May  8 22:34:55 iFourS com.apple.xpc.launchd[1] (UIKitApplication:com.ulangi.Ulangi[0xc011][648]) <Notice>: Service exited due to signal: Abort trap: 6