fix crash on project close from deleting events

include/core/events.h

@@ -7,6 +7,7 @@
 #include <QSet>
 #include <QPixmap>
 #include <QJsonObject>
+#include <QPointer>
 
 #include "orderedjson.h"
 using OrderedJson = poryjson::Json;
@@ -198,7 +199,7 @@ protected:
     QPixmap pixmap;
     DraggablePixmapItem *pixmapItem = nullptr;
 
-    EventFrame *eventFrame = nullptr;
+    QPointer<EventFrame> eventFrame;
 };