do not set initialdata if user is undefined (#521)

Author: jhuleatt

src/auth.tsx

@@ -24,15 +24,15 @@ export function useUser<T = unknown>(options?: ReactFireOptions<T>): ObservableS
 
   const observableId = `auth:user:${auth.name}`;
   const observable$ = user(auth);
+  const _options: ReactFireOptions<T> = {...options} ?? {};
 
-  let currentUser = auth.currentUser;
-
-  // Only use options.initialData if auth.currentUser is unavailable
-  if (!currentUser && (options?.initialData ?? options?.startWithValue)) {
-    currentUser = options.initialData ?? options.startWithValue;
+  // only set/override initialData if auth has finished loading
+  if (auth.currentUser !== undefined) {
+    _options.initialData = auth.currentUser;
+    _options.startWithValue = auth.currentUser;
   }
 
-  return useObservable(observableId, observable$, { ...options, initialData: currentUser });
+  return useObservable(observableId, observable$, _options);
 }
 
 export function useIdTokenResult(user: User, forceRefresh: boolean = false, options?: ReactFireOptions<IdTokenResult>): ObservableStatus<IdTokenResult> {