fix welcome page title fixes #4273

modules/UI/UI.js

  * established, false - otherwise (for example in the case of welcome page)
  */
 UI.start = function() {
-    document.title = interfaceConfig.APP_NAME;
-
     // Set the defaults for prompt dialogs.
     $.prompt.setDefaults({ persistent: false });
 
         APP.store.dispatch(setNotificationsEnabled(false));
         UI.messageHandler.enablePopups(false);
     }
-
-    document.title = interfaceConfig.APP_NAME;
 };
 
 /**

react/features/conference/components/web/Conference.js

      * @inheritdoc
      */
     componentDidMount() {
+        document.title = interfaceConfig.APP_NAME;
+
         const { configLocation } = config;
 
         if (configLocation) {

react/features/welcome/components/WelcomePage.web.js

      */
     componentDidMount() {
         document.body.classList.add('welcome-page');
+        document.title = interfaceConfig.APP_NAME;
 
         if (this.state.generateRoomnames) {
             this._updateRoomname();