QmlDesigner: Do not dispatch commands when already in destructor

On Linux destructing the local sockets leads to commands being
dispatched synchronously. This is not expected and totally unrequired.
When we shutdown the instance server no commands have to be dispatched
anymore.

Change-Id: Ieeca7ac2103e7b463137d76f85cd326888cc38ce
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/qmldesigner/designercore/instances/nodeinstanceserverproxy.cpp

@@ -225,6 +225,8 @@ NodeInstanceServerProxy::NodeInstanceServerProxy(NodeInstanceView *nodeInstanceV
 
 NodeInstanceServerProxy::~NodeInstanceServerProxy()
 {
+    m_destructing = true;
+
     disconnect(this, SLOT(processFinished(int,QProcess::ExitStatus)));
 
     writeCommand(QVariant::fromValue(EndPuppetCommand()));
@@ -273,6 +275,9 @@ void NodeInstanceServerProxy::dispatchCommand(const QVariant &command, PuppetStr
     static const int debugOutputCommandType = QMetaType::type("DebugOutputCommand");
     static const int puppetAliveCommandType = QMetaType::type("PuppetAliveCommand");
 
+    if (m_destructing)
+        return;
+
     qCInfo(instanceViewBenchmark) << "dispatching command" << command.userType() << command.typeName();
     if (command.userType() ==  informationChangedCommandType) {
         nodeInstanceClient()->informationChanged(command.value<InformationChangedCommand>());

src/plugins/qmldesigner/designercore/instances/nodeinstanceserverproxy.h

@@ -128,6 +128,7 @@ private:
     RunModus m_runModus;
     int m_synchronizeId = -1;
     QTime m_benchmarkTimer;
+    bool m_destructing = false;
 };
 
 } // namespace QmlDesigner