fix(filmstrip): do not show video for large video speaker in audio only

When in audio only, the video should not be shown and instead the
avatar should display.

modules/UI/videolayout/SmallVideo.js

 SmallVideo.prototype.selectDisplayMode = function() {
     // Display name is always and only displayed when user is on the stage
     if (this.isCurrentlyOnLargeVideo()) {
-        return this.isVideoPlayable()
+        return this.isVideoPlayable() && !APP.conference.isAudioOnly()
             ? DISPLAY_BLACKNESS_WITH_NAME : DISPLAY_AVATAR_WITH_NAME;
     } else if (this.isVideoPlayable()
         && this.selectVideoElement().length