Fix undefined in client startup

bigbluebutton-html5/imports/ui/components/modal/fullscreen/component.jsx

@@ -49,6 +49,7 @@ const defaultProps = {
     disabled: false,
   },
   dismiss: {
+    callback: () => {},
     disabled: false,
   },
   preventClosing: false,

bigbluebutton-html5/imports/ui/components/modal/simple/component.jsx

@@ -37,7 +37,12 @@ class ModalSimple extends Component {
   }
 
   handleDismiss() {
-    this.props.modalHide(this.props.dismiss.callback);
+    const {
+      modalHide,
+      dismiss,
+    } = this.props;
+    if (!dismiss && !modalHide) return;
+    modalHide(dismiss.callback);
   }
 
   render() {