fix bug of shell having a copy of engine instead of reference

src/sparrowshell/scriptnode.cpp

@@ -40,7 +40,7 @@ ScriptNode::ScriptNode()
 void ScriptNode::update(){
     static bool test = true;
     if(test && getScene() != nullptr){
-        m_script["engine"] = getEngine();
+        m_script["engine"] = &getEngine();
         test=false;
     }
 }