send redis msg when stopping external video due to screenshare

bigbluebutton-html5/imports/api/screenshare/server/handlers/screenshareStarted.js

@@ -1,16 +1,20 @@
 import { check } from 'meteor/check';
 import Meetings from '/imports/api/meetings';
+import Users from '/imports/api/users';
 import addScreenshare from '../modifiers/addScreenshare';
 import Logger from '/imports/startup/server/logger';
+import stopWatchingExternalVideo from '/imports/api/external-videos/server/methods/stopWatchingExternalVideo';
 
 export default function handleScreenshareStarted({ body }, meetingId) {
   check(meetingId, String);
   check(body, Object);
 
   const meeting = Meetings.findOne({ meetingId });
+  const presenter = Users.findOne({ meetingId, presenter: true });
+  const presenterId = presenter && presenter.userId ? presenter.userId : 'system-screenshare-starting';
   if (meeting && meeting.externalVideoUrl) {
     Logger.info(`ScreenshareStarted: There is external video being shared. Stopping it due to presenter change, ${meeting.externalVideoUrl}`);
-    Meetings.update({ meetingId }, { $set: { externalVideoUrl: null } });
+    stopWatchingExternalVideo({ meetingId, requesterUserId: presenterId });
   }
   return addScreenshare(meetingId, body);
 }