Skip linking for anonymous users
Skip linking for anonymous users

Should fix #357 and #389 and maybe others as well.

This will avoid the exception `com.google.firebase.auth.FirebaseAuthUserCollisionException: This credential is already associated with a different user account`.

This problem occurs if the current user is anonymous, but the `loginResult` points to another already known firebase user (e.g a facebook account). In this case we have to call `firebaseAuth.signInWithCredential(authCredential).addOnCompleteListener(onCompleteListener)` instead of `user.linkWithCredential(authCredential).addOnCompleteListener(onCompleteListener)`
EddyVerbruggen/nativescript-plugin-firebase,EddyVerbruggen/nativescript-plugin-firebase,EddyVerbruggen/nativescript-plugin-firebase,EddyVerbruggen/nativescript-plugin-firebase,EddyVerbruggen/nativescript-plugin-firebase,EddyVerbruggen/nativescript-plugin-firebase