flip the authentication state

src/Client/src/app/services/Authentication.ts

@@ -31,7 +31,7 @@ export class Authentication{
     }
 
     get isLoggedIn(): boolean {
-        return this._user.value.id == null ? true : false;
+        return this._user.value.id != null ? true : false;
     }
 
     get loggedInUser(): Account {