Fix a minor bug on program shutdown with link deletion

src/QGCCore.cc

@@ -206,9 +206,12 @@ QGCCore::~QGCCore()
     mainWindow->close();
     //mainWindow->deleteLater();
     // Delete singletons
-	delete MainWindow::instance();
-    delete LinkManager::instance();
+    // First systems
     delete UASManager::instance();
+    // then links
+    delete LinkManager::instance();
+    // Finally the main window
+	delete MainWindow::instance();
 }
 
 /**

src/comm/QGCXPlaneLink.cc

@@ -54,11 +54,10 @@ QGCXPlaneLink::QGCXPlaneLink(UASInterface* mav, QString remoteHost, QHostAddress
 }
 
 QGCXPlaneLink::~QGCXPlaneLink()
-{   //do not disconnect unless it is connected.
-    //disconnectSimulation will delete the memory that was allocated for proces, terraSync and socket
-    if(connectState){
-       disconnectSimulation();
-    }
+{
+//    if(connectState) {
+//       disconnectSimulation();
+//    }
 }
 
 /**

src/uas/UAS.cc

@@ -1647,14 +1647,13 @@ void UAS::setMode(int mode)
 */
 void UAS::sendMessage(mavlink_message_t message)
 {
+    if (!LinkManager::instance()) return;
     // Emit message on all links that are currently connected
     foreach (LinkInterface* link, *links)
     {
-        //qDebug() << "ITERATING THROUGH LINKS";
         if (LinkManager::instance()->getLinks().contains(link))
         {
             sendMessage(link, message);
-            //qDebug() << "SENT MESSAGE";
         }
         else
         {