Flutter Firebase Authentication app crashes after creating user - flutter

Question

I've been using firebase services for quite some time.
So i started a new flutter project yesterday and i'm experiencing app crashes, some times when when a user registers an account With Firebase Auth. according to console log, its probably because of invoking onAuthStateChanged.
Can anyone help me resolve this.
NB: Sometimes an account is created successfully without the app crashing.
This is the code where i call onAuthStateChanged :
User _userFromFirebase(FirebaseUser user){
return user != null ? User(uid: user.uid, email: user.email, name: user.displayName, phoneNo: user.phoneNumber)
: null ;
}
Stream<User> get user {
return _auth.onAuthStateChanged.map(_userFromFirebase);
}
Below is the debug console output;
D/FirebaseAuth(14930): Notifying id token listeners about user ( VZcLcnr4dJOZgLjFYU3ls96yHK13 ).
D/FirebaseAuth(14930): Notifying auth state listeners about user ( VZcLcnr4dJOZgLjFYU3ls96yHK13 ).
D/AndroidRuntime(14930): Shutting down VM
E/AndroidRuntime(14930): FATAL EXCEPTION: main
E/AndroidRuntime(14930): Process: com.tonnyapps.app3, PID: 14930
E/AndroidRuntime(14930): java.lang.NullPointerException: Attempt to invoke virtual method 'void io.flutter.plugin.common.MethodChannel.invokeMethod(java.lang.String, java.lang.Object)' on a null object reference
E/AndroidRuntime(14930): at io.flutter.plugins.firebaseauth.FirebaseAuthPlugin$3.onAuthStateChanged(FirebaseAuthPlugin.java:710)
E/AndroidRuntime(14930): at com.google.firebase.auth.zzp.run(com.google.firebase:firebase-auth##19.2.0:3)
E/AndroidRuntime(14930): at android.os.Handler.handleCallback(Handler.java:873)
E/AndroidRuntime(14930): at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(14930): at com.google.android.gms.internal.firebase_auth.zzj.dispatchMessage(com.google.firebase:firebase-auth##19.2.0:6)
E/AndroidRuntime(14930): at android.os.Looper.loop(Looper.java:214)
E/AndroidRuntime(14930): at android.app.ActivityThread.main(ActivityThread.java:7050)
E/AndroidRuntime(14930): at java.lang.reflect.Method.invoke(Native Method)
E/AndroidRuntime(14930): at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494)
E/AndroidRuntime(14930): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965)
I/Process (14930): Sending signal. PID: 14930 SIG: 9
Lost connection to device.

Answer 1

After many efforts tweaking around with the code and updating dependencies to support higher versions of firebase_auth. I was able to upgrade and fix the version of firebase_auth to version 0.20.1, since it was the last non null-safe version.
And Wallah, it worked, this must have been a bug with whatever version i was using. But it was solved with later releases. The users can now create users successfully and proceed with the normal app flow.
So setting firebase_auth: 0.20.1 in the pubspec.yaml, worked for me.

Answer 2

Since, the project is old, I would recommend the best option is updating all the code, and preferably migrating the project to null safety. This should give you more control over the project future development, and also probably fix the bugs you are experiencing with the old code.