Be more defensive when tearing down

- Move the original m_toolviews as it gets modified on destruction
- Use QPointer for storing toolviews

apps/lib/katemdi.cpp

@@ -1322,8 +1322,10 @@ MainWindow::MainWindow(QWidget *parentWidget)
 
 MainWindow::~MainWindow()
 {
-    // cu toolviews
-    qDeleteAll(m_toolviews);
+    // move toolviews as deleting them will
+    // modify m_toolviews. see toolViewDeleted
+    auto toolviews = m_toolviews;
+    qDeleteAll(toolviews);
 
     // seems like we really should delete this by hand ;)
     delete m_centralWidget;

apps/lib/katemdi.h

@@ -589,12 +589,12 @@ private:
     /**
      * map identifiers to widgets
      */
-    std::map<QString, ToolView *> m_idToWidget;
+    std::map<QString, QPointer<ToolView>> m_idToWidget;
 
     /**
      * list of all toolviews around
      */
-    std::vector<ToolView *> m_toolviews;
+    std::vector<QPointer<ToolView>> m_toolviews;
 
     /**
      * widget, which is the central part of the