event fixes: crashed when the obj was deleted in nested events

src/lv_core/lv_obj.h

@@ -571,6 +571,15 @@ lv_res_t lv_event_send(lv_obj_t * obj, lv_event_t event, const void * data);
  */
 const void * lv_event_get_data(void);
 
+/**
+ * Mark the current object in the event as deleted.
+ * It not required in the general cases because the library will take care of it.
+ * However if an event is sent manually to an other object from an event where the object is deleted
+ * the library will not know about the deletion (because it happened in an other object's event).
+ * In this specific case the object need to be marked as deleted manually.
+ */
+void lv_event_mark_as_deleted(void);
+
 /**
  * Set the a signal function of an object. Used internally by the library.
  * Always call the previous signal function in the new.