Clang: Stop sending data to backend on disconnect

This addresses

    SOFT ASSERT made fatal: "m_connection.isConnected()" in file
      src/plugins/clangcodemodel/clangbackendipcintegration.cpp, line 230

I could not reproduce the issue locally, so I'm leaving the soft asserts
untouched for now.

Change-Id: If1d55ba7bc7e2d1ac20ad992c6d0d43ceb0f5d73
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/libs/clangbackendipc/connectionclient.cpp

@@ -51,6 +51,7 @@ ConnectionClient::ConnectionClient()
 
     connectLocalSocketError();
     connectLocalSocketConnected();
+    connectLocalSocketDisconnected();
 }
 
 void ConnectionClient::startProcessAndConnectToServerAsynchronously()
@@ -230,6 +231,14 @@ void ConnectionClient::connectLocalSocketConnected()
             &ConnectionClient::resetProcessIsStarting);
 }
 
+void ConnectionClient::connectLocalSocketDisconnected()
+{
+    connect(&localSocket,
+            &QLocalSocket::disconnected,
+            this,
+            &ConnectionClient::disconnectedFromLocalSocket);
+}
+
 void ConnectionClient::finishProcess()
 {
     finishProcess(std::move(process_));

src/libs/clangbackendipc/connectionclient.h

@@ -76,6 +76,7 @@ public:
 
 signals:
     void connectedToLocalSocket();
+    void disconnectedFromLocalSocket();
     void processFinished();
 
 protected:
@@ -102,6 +103,7 @@ private:
     void printStandardError();
 
     void connectLocalSocketConnected();
+    void connectLocalSocketDisconnected();
     void connectProcessFinished(QProcess *process) const;
     void connectProcessStarted(QProcess *process) const;
     void disconnectProcessFinished(QProcess *process) const;