fix double callback issue on signInWithEmail

Author: Salakar

android/src/main/java/io/fullstack/firestack/FirestackAuth.java

@@ -61,16 +61,16 @@ public String getName() {
 
   @ReactMethod
   public void listenForAuth() {
-    if (mAuthListener == null) {
+    if (mAuthListener == null || mAuth == null) {
       mAuthListener = new FirebaseAuth.AuthStateListener() {
         @Override
         public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
           WritableMap msgMap = Arguments.createMap();
           msgMap.putString("eventName", "listenForAuth");
 
           if (FirestackAuthModule.this.user != null) {
+            // TODO move to helper
             WritableMap userMap = getUserMap();
-
             msgMap.putBoolean("authenticated", true);
             msgMap.putMap("user", userMap);
 
@@ -92,6 +92,7 @@ public void unlistenForAuth(final Callback callback) {
     if (mAuthListener != null) {
       mAuth.removeAuthStateListener(mAuthListener);
 
+      // TODO move to helper
       WritableMap resp = Arguments.createMap();
       resp.putString("status", "complete");
 
@@ -140,12 +141,6 @@ public void onComplete(@NonNull Task<AuthResult> task) {
               userExceptionCallback(ex, callback);
             }
           }
-        })
-        .addOnFailureListener(new OnFailureListener() {
-          @Override
-          public void onFailure(@NonNull Exception ex) {
-            userExceptionCallback(ex, callback);
-          }
         });
   }