Apply suggestions from code review

Co-authored-by: Saúl Ibarra Corretgé <saghul@jitsi.org>

react/features/filmstrip/components/native/Thumbnail.js

         = getTrackByMediaTypeAndParticipant(tracks, MEDIA_TYPE.AUDIO, id);
     const videoTrack
         = getTrackByMediaTypeAndParticipant(tracks, MEDIA_TYPE.VIDEO, id);
-    const videoMuted = !videoTrack || videoTrack.muted;
-    const isScreenShare = videoTrack && videoTrack.videoType === VIDEO_TYPE.DESKTOP;
+    const videoMuted = videoTrack?.muted ?? true;
+    const isScreenShare = videoTrack?.videoType === VIDEO_TYPE.DESKTOP;
     const participantCount = getParticipantCount(state);
     const renderDominantSpeakerIndicator = participant && participant.dominantSpeaker && participantCount > 2;
     const _isEveryoneModerator = isEveryoneModerator(state);
     const renderModeratorIndicator = !_isEveryoneModerator
-        && participant && participant.role === PARTICIPANT_ROLE.MODERATOR;
+        && participant?.role === PARTICIPANT_ROLE.MODERATOR;
     const participantInLargeVideo = id === largeVideo.participantId;
 
     return {