fix(auth, android): avoid crash on react-native < 0.63

At minimum phone OTP auth and perhaps other scenarios may crash on
very old react-native, because old react-native used to throw an exception
if a map didn't contain a key, whereas newer react-native just returns null

Newer code here related to multi-factor auth relied on that returns-null
behavior and did not handle the case where an exception may be thrown if
a key didn't exist

Avoid this exception+crash by explicitly checking for our desired key prior to
getting its value

packages/auth/android/src/main/java/io/invertase/firebase/auth/ReactNativeFirebaseAuthModule.java

@@ -1944,7 +1944,10 @@ private void promiseWithAuthResult(AuthResult authResult, Promise promise) {
    */
   private void promiseRejectAuthException(Promise promise, Exception exception) {
     WritableMap error = getJSError(exception);
-    final String sessionId = error.getString("sessionId");
+    String sessionId = null;
+    if (error.hasKey("sessionId")) {
+      sessionId = error.getString("sessionId");
+    }
     final MultiFactorResolver multiFactorResolver = mCachedResolvers.get(sessionId);
     WritableMap resolverAsMap = Arguments.createMap();
     if (multiFactorResolver != null) {