[chore] - Fix typing errors

Author: KkevinLi

src/app/auth/index.ts

@@ -4,7 +4,7 @@ import { FirebaseEmailLinkActionCodeSettings, LoginType, User } from "../../fire
 export module auth {
   export class Auth {
     private authStateChangedHandler;
-    public currentUser: User;
+    public currentUser: User | undefined;
     public languageCode: string | null;
 
     public onAuthStateChanged(handler: (user: User) => void): void {

src/app/database/index.ts

@@ -1,5 +1,4 @@
 import * as firebase from "../../firebase";
-import { AddEventListenerResult, FBData } from "../../firebase";
 import { nextPushId } from "./util/NextPushId";
 
 export namespace database {
@@ -94,7 +93,7 @@ export namespace database {
      * Creates a Query with the specified starting point. The value to start at should match the type
      * passed to orderBy(). If using orderByKey(), the value must be a string
      */
-    public startAt(value: number | string | boolean | null): firebase.Query {
+    public startAt(value: number | string | boolean): firebase.Query {
       return this.queryObject.startAt(value);
     }
 

src/app/storage/index.ts

@@ -11,7 +11,7 @@ export module storage {
 
   export class Reference {
 
-    private path: string;
+    private path: string | undefined;
 
     parent: Reference | null; // TODO set this every time we navigate..
     root: Reference;