feat(virtual-background): Desktop share as virtual background

lang/main.json

         "slightBlur": "Slight Blur",
         "removeBackground": "Remove background",
         "addBackground": "Add background",
-        "none": "None"
+        "none": "None",
+        "desktopShareError": "Could not create desktop share"
     },
     "feedback": {
         "average": "Average",

react/features/virtual-background/components/VirtualBackgroundDialog.js

 import { VIDEO_TYPE } from '../../base/media';
 import { connect } from '../../base/redux';
 import { getLocalVideoTrack } from '../../base/tracks';
+import { showErrorNotification } from '../../notifications';
 import { toggleBackgroundEffect } from '../actions';
 import { VIRTUAL_BACKGROUND_TYPE } from '../constants';
 import { resizeImage, toDataURL } from '../functions';
         const url = await createLocalTrack('desktop', '');
 
         if (!url) {
-            throw new Error('Could not create desktop local track!');
+            dispatch(showErrorNotification({
+                titleKey: 'virtualBackground.desktopShareError'
+            }));
+            logger.error('Could not create desktop share as a virtual background!');
+
+            return;
         }
         setOptions({
             backgroundType: VIRTUAL_BACKGROUND_TYPE.DESKTOP_SHARE,

react/features/virtual-background/middleware.js

     const virtualSource = getState()['features/virtual-background'].virtualSource;
     const currentLocalTrack = getLocalVideoTrack(getState()['features/base/tracks']);
 
-    if (virtualSource?.videoType === VIDEO_TYPE.DESKTOP && currentLocalTrack) {
-        localTrackStopped(dispatch, virtualSource, currentLocalTrack.jitsiTrack);
+    if (virtualSource?.videoType === VIDEO_TYPE.DESKTOP) {
+        localTrackStopped(dispatch, virtualSource, currentLocalTrack?.jitsiTrack);
     }
 
     return next(action);