增加判空逻辑

teacher/src/main/java/com/cooleshow/teacher/presenter/live/LiveRoomPresenter.java

@@ -459,6 +459,9 @@ public class LiveRoomPresenter extends BasePresenter<LiveRoomContract.LiveRoomVi
      */
     public void startPublish() {
         RCRTCRoom rcrtcRoom = LiveEventHelper.getInstance().getRtcRoom();
+        if (rcrtcRoom == null) {
+            return;
+        }
         RCRTCEngine.getInstance().getDefaultVideoStream().startCamera(null);
         rcrtcRoom.getLocalUser().publishDefaultLiveStreams(new IRCRTCResultDataCallback<RCRTCLiveInfo>() {
             @Override