rtmp session when client stop publish not set push src null avoid judge player or pusher error

src/Rtmp/RtmpSession.cpp

@@ -222,7 +222,7 @@ void RtmpSession::onCmd_deleteStream(AMFDecoder &dec) {
     sendStatus({ "level", "status",
                  "code", "NetStream.Unpublish.Success",
                  "description", "Stop publishing." });
-    _push_src = nullptr;
+    //_push_src = nullptr;
     throw std::runtime_error(StrPrinter << "Stop publishing" << endl);
 }