fix crash when just clicking a layer-move-button

GUI/View/SampleDesigner/WidgetMoverButton.cpp

@@ -23,6 +23,7 @@
 WidgetMoverButton::WidgetMoverButton(QWidget* parent, QWidget* widgetToMove, int ignoreOnTop)
     : QToolButton(parent)
     , m_widgetToMove(widgetToMove)
+    , m_dropAboveThisWidget(nullptr)
     , m_ignoreOnTop(ignoreOnTop)
     , m_scrollArea(nullptr)
 {
@@ -48,6 +49,9 @@ void WidgetMoverButton::mousePressEvent(QMouseEvent* event)
 
 void WidgetMoverButton::mouseReleaseEvent(QMouseEvent*)
 {
+    if (!m_started)
+        return;
+
     qDeleteAll(m_animations.values());
     m_animations.clear();