fix: video muted out of sync

When video is unmuted when toggling off the audio only mode it
dispatches video muted status, but does not roll it back in case it
fails. That was causing toolbar button on Web to display incorrect
video muted status.

conference.js

  * result of user interaction
  */
 function muteLocalAudio(muted) {
-    muteLocalMedia(localAudio, muted, 'Audio');
+    muteLocalMedia(localAudio, muted);
 }
 
-function muteLocalMedia(localMedia, muted, localMediaTypeString) {
-    if (!localMedia) {
-        return;
+/**
+ * Mute or unmute local media stream if it exists.
+ * @param {JitsiLocalTrack} localTrack
+ * @param {boolean} muted
+ *
+ * @returns {Promise} resolved in case mute/unmute operations succeeds or
+ * rejected with an error if something goes wrong. It is expected that often
+ * the error will be of the {@link JitsiTrackError} type, but it's not
+ * guaranteed.
+ */
+function muteLocalMedia(localTrack, muted) {
+    if (!localTrack) {
+        return Promise.resolve();
     }
 
     const method = muted ? 'mute' : 'unmute';
 
-    localMedia[method]().catch(reason => {
-        logger.warn(`${localMediaTypeString} ${method} was rejected:`, reason);
-    });
+    return localTrack[method]();
 }
 
 /**
  * Mute or unmute local video stream if it exists.
  * @param {boolean} muted if video stream should be muted or unmuted.
+ *
+ * @returns {Promise} resolved in case mute/unmute operations succeeds or
+ * rejected with an error if something goes wrong. It is expected that often
+ * the error will be of the {@link JitsiTrackError} type, but it's not
+ * guaranteed.
  */
 function muteLocalVideo(muted) {
-    muteLocalMedia(localVideo, muted, 'Video');
+    return muteLocalMedia(localVideo, muted);
 }
 
 /**
             return;
         }
 
+        const maybeShowErrorDialog = (error) => {
+            if (showUI) {
+                APP.UI.showDeviceErrorDialog(null, error);
+            }
+        };
+
         if (!localVideo && this.videoMuted && !mute) {
             // Try to create local video if there wasn't any.
             // This handles the case when user joined with no video
                 .then(([videoTrack]) => videoTrack)
                 .catch(error => {
                     // FIXME should send some feedback to the API on error ?
-                    if (showUI) {
-                        APP.UI.showDeviceErrorDialog(null, error);
-                    }
+                    maybeShowErrorDialog(error);
+
                     // Rollback the video muted status by using null track
                     return null;
                 })
                 .then(videoTrack => this.useVideoStream(videoTrack));
         } else {
-            // FIXME if localVideo exists and the permissions are blocked
-            // while video muted it will fail to unmute and UI will get out of
-            // sync (the toolbar will show unmuted even though unmute failed).
-            // But for some reason that only happens when toggling off from
-            // the audio only mode - the same scenario works fine from toolbar.
-            // This is very rare corner case and supposedly this will get fixed
-            // once everything goes to react/redux.
-            muteLocalVideo(mute);
+            const oldMutedStatus = this.videoMuted;
+
+            muteLocalVideo(mute)
+                .catch(error => {
+                    maybeShowErrorDialog(error);
+                    this.videoMuted = oldMutedStatus;
+                    APP.UI.setVideoMuted(this.getMyUserId(), this.videoMuted);
+                });
         }
     },
     /**