[js] misc flow fixes in auth

lib/flow.js

@@ -7,7 +7,7 @@ declare module 'react-native' {
 declare type AuthResultType = {
   authenticated: boolean,
   user: Object|null
-};
+} | null;
 
 declare type CredentialType = {
   provider: string,

lib/modules/auth/index.js

@@ -3,7 +3,7 @@ import { NativeModules, NativeEventEmitter } from 'react-native';
 
 import User from './user';
 import { Base } from './../base';
-import EmailAuthProvider from './Email';
+import EmailAuthProvider from './providers/Email';
 
 const FirebaseAuth = NativeModules.RNFirebaseAuth;
 const FirebaseAuthEvt = new NativeEventEmitter(FirebaseAuth);
@@ -36,7 +36,7 @@ export default class Auth extends Base {
    * @param emit
    * @private
    */
-  _onAuthStateChanged(auth: AuthResultType, emit: Boolean = true) {
+  _onAuthStateChanged(auth: AuthResultType, emit: boolean = true) {
     this._authResult = auth;
     this.authenticated = auth ? auth.authenticated || false : false;
     if (auth && auth.user && !this._user) this._user = new User(this, auth);
@@ -67,7 +67,7 @@ export default class Auth extends Base {
     return promise.then((result) => {
       if (!result) return this._onAuthStateChanged(null, false);
       if (result.user) return this._onAuthStateChanged(result, false);
-      if (result.uid) return this._onAuthStateChanged({ user: result }, false);
+      if (result.uid) return this._onAuthStateChanged({ authenticated: true, user: result }, false);
       return result;
     });
   }