Send NString to a reject function instead of NSException. React-Native 0.79

[KorotkovAlex]

In react-native 0.79 reject interface are changed. We should send NSString instead of NSException

[jankosecki]

I can confirm - reject on 0.79 bridgeless crashes the app if NSException is passed instead of NSString.
Changing to e.description has fixed it for me.

Also, API of reject has expected NSString for few years already so it means that the mapping layer has become stricter in 0.79 but merging it shouldn't cause any problems on older versions

[octaviotastico]

We encountered a very similar crash in an Expo SDK 56 application using React Native 0.85.3 with the New Architecture enabled.

The crash occurred when an iOS audio route operation failed inside setAudioRoute or getAudioRoutes. RNCallKeep passed the caught NSException directly as the Promise rejection message. With the newer React Native TurboModule error conversion, the runtime expected an NSString and attempted to call UTF8String on the NSException, resulting in:

-[NSException UTF8String]: unrecognized selector sent to instance

Our local workaround was to pass e.description (or an equivalent NSString) to reject instead of the exception object. We also delayed application-level audio route changes until didActivateAudioSession, since CallKit may not have activated the AVAudioSession yet. The latter is app-side timing, but the rejection conversion is a library issue.

This PR would help us and other applications using current React Native versions significantly. Thank you for putting together the fix.