Fix shutdown crash

src/QGCApplication.cc

@@ -334,8 +334,12 @@ QGCApplication::QGCApplication(int &argc, char* argv[], bool unitTesting)
     _toolbox->setChildToolboxes();
 }
 
-QGCApplication::~QGCApplication()
+void QGCApplication::_shutdown(void)
 {
+    // This code is specifically not in the destructor since the application object may not be available in the destructor.
+    // This cause problems for deleting object like settings which are in the toolbox which may have qml references. By
+    // moving them here and having main.cc call this prior to deleting the app object we make sure app object is still
+    // around while these things are shutting down.
 #ifndef __mobile__
     MainWindow* mainWindow = MainWindow::instance();
     if (mainWindow) {
@@ -346,6 +350,11 @@ QGCApplication::~QGCApplication()
     delete _toolbox;
 }
 
+QGCApplication::~QGCApplication()
+{
+    // Place shutdown code in _shutdown
+}
+
 void QGCApplication::_initCommon(void)
 {
     QSettings settings;

src/QGCApplication.h

@@ -152,6 +152,12 @@ public:
 
     static QGCApplication*  _app;   ///< Our own singleton. Should be reference directly by qgcApp
 
+public:
+    // Although public, these methods are internal and should only be called by UnitTest code
+
+    /// Shutdown the application object
+    void _shutdown(void);
+
 private slots:
     void _missingParamsDisplay(void);
 

src/main.cc

@@ -253,6 +253,7 @@ int main(int argc, char *argv[])
         exitCode = app->exec();
     }
 
+    app->_shutdown();
     delete app;
     //-- Shutdown Cache System
     destroyMapEngine();