src: Fixed crash when using shortcuts with focus on the graph (issue #390)

bug id = 390

src/lib_gui/qt/graphics/QtGraphicsView.cpp

@@ -195,7 +195,7 @@ void QtGraphicsView::mouseReleaseEvent(QMouseEvent *event)
 
 void QtGraphicsView::keyPressEvent(QKeyEvent* event)
 {
-	if (event->key() >= Qt::Key_A && event->key() <= Qt::Key_Z)
+	if (event->key() >= Qt::Key_A && event->key() <= Qt::Key_Z && event->text().size())
 	{
 		QChar c = event->text().at(0).toUpper();
 		emit characterKeyPressed(c);

src/lib_gui/qt/window/QtMainWindow.h

@@ -78,7 +78,7 @@ protected:
 	void keyPressEvent(QKeyEvent* event);
 	void contextMenuEvent(QContextMenuEvent* event);
 	void closeEvent(QCloseEvent* event);
-    void resizeEvent(QResizeEvent* event) override;
+    void resizeEvent(QResizeEvent* event);
 
 public slots:
 	void about();