Fixes JS error when muting video.

lib-jitsi-meet.js

     } else {
         if (mute) {
             this.dontFireRemoveEvent = true;
-            this.rtc.room.removeStream(this.stream);
+            this.rtc.room.removeStream(this.stream, function () {});
             RTC.stopMediaStream(this.stream);
             if(isAudio)
                 this.rtc.room.setAudioMute(mute);

modules/RTC/JitsiLocalTrack.js

     } else {
         if (mute) {
             this.dontFireRemoveEvent = true;
-            this.rtc.room.removeStream(this.stream);
+            this.rtc.room.removeStream(this.stream, function () {});
             RTC.stopMediaStream(this.stream);
             if(isAudio)
                 this.rtc.room.setAudioMute(mute);