message: Don't remove call when we call hangup
  as hopefully explained by comment
diff: @@ -566,7 +566,8 @@ export default class CallHandler {
  } else {
  this.calls.get(payload.room_id).hangup(CallErrorCode.UserHangup, false);
  }
  - this.removeCallForRoom(payload.room_id);
  + // don't remove the call yet: let the hangup event handler do it (otherwise it will throw
  + // the hangup event away)
  break;
  case 'answer': {
  if (!this.calls.has(payload.room_id)) {
  