Fix start_sso / start_cas URLs failing to redirect to a authentication prompt (#11681)

* Show screen before login if using start_sso or start_cas

* Add tests

* Fix lint

* Fix lint

* Add one for CAS

* prettier

src/components/structures/MatrixChat.tsx

@@ -393,7 +393,8 @@ export default class MatrixChat extends React.PureComponent<IProps, IState> {
             return;
         }
 
-        if (firstScreen === "login" || firstScreen === "register" || firstScreen === "forgot_password") {
+        // If the first screen is an auth screen, we don't want to wait for login.
+        if (firstScreen !== null && AUTH_SCREENS.includes(firstScreen)) {
             this.showScreenAfterLogin();
         }
     }