logic: Fixed crash when closing license window on force entering license

src/lib_gui/qt/window/QtMainWindow.cpp

@@ -63,14 +63,25 @@ QtViewToggle::QtViewToggle(View* view, QWidget *parent)
 {
 }
 
+void QtViewToggle::clear()
+{
+	m_view = nullptr;
+}
+
 void QtViewToggle::toggledByAction()
 {
-	dynamic_cast<QtMainWindow*>(parent())->toggleView(m_view, true);
+	if (m_view)
+	{
+		dynamic_cast<QtMainWindow*>(parent())->toggleView(m_view, true);
+	}
 }
 
 void QtViewToggle::toggledByUI()
 {
-	dynamic_cast<QtMainWindow*>(parent())->toggleView(m_view, false);
+	if (m_view)
+	{
+		dynamic_cast<QtMainWindow*>(parent())->toggleView(m_view, false);
+	}
 }
 
 
@@ -149,6 +160,11 @@ QtMainWindow::~QtMainWindow()
 	{
 		delete [] m_recentProjectAction;
 	}
+
+	for (DockWidget& dockWidget : m_dockWidgets)
+	{
+		dockWidget.toggle->clear();
+	}
 }
 
 void QtMainWindow::addView(View* view)

src/lib_gui/qt/window/QtMainWindow.h

@@ -23,6 +23,7 @@ class QtViewToggle
 
 public:
 	QtViewToggle(View* view, QWidget *parent = nullptr);
+	void clear();
 
 public slots:
 	void toggledByAction();