修复空指针异常

src/main/java/com/genersoft/iot/vmp/gb28181/service/impl/PlayServiceImpl.java

@@ -342,7 +342,9 @@ public class PlayServiceImpl implements IPlayService {
                 MediaServer mediaInfo = streamInfo.getMediaServer();
                 Boolean ready = mediaServerService.isStreamReady(mediaInfo, "rtp", streamId);
                 if (ready != null && ready) {
-                    callback.run(InviteErrorCode.SUCCESS.getCode(), InviteErrorCode.SUCCESS.getMsg(), streamInfo);
+                    if(callback != null) {
+                        callback.run(InviteErrorCode.SUCCESS.getCode(), InviteErrorCode.SUCCESS.getMsg(), streamInfo);
+                    }
                     inviteStreamService.call(InviteSessionType.PLAY, channel.getId(), null,
                             InviteErrorCode.SUCCESS.getCode(),
                             InviteErrorCode.SUCCESS.getMsg(),