fix(filmstrip_only): JS errors

conference.js

                 this.isDesktopSharingEnabled =
                     JitsiMeetJS.isDesktopSharingEnabled();
 
-                if (UIUtil.isButtonEnabled('contacts'))
+                if (UIUtil.isButtonEnabled('contacts')
+                    && !interfaceConfig.filmStripOnly) {
                     APP.UI.ContactList = new ContactList(room);
+                }
 
                 // if user didn't give access to mic or camera or doesn't have
                 // them at all, we disable corresponding toolbar buttons

modules/UI/videolayout/VideoLayout.js

         // Update the large video if the video source is already available,
         // otherwise wait for the "videoactive.jingle" event.
         // FIXME: there is no "videoactive.jingle" event.
-        if (!pinnedId
+        if (!interfaceConfig.filmStripOnly && !pinnedId
             && remoteVideo.hasVideoStarted()
             && !this.getCurrentlyOnLargeContainer().stayOnStage()) {
             this.updateLargeVideo(id);