Hiding an item in a QTreeWidget and then drag a remaining visible one could cause an 'index out of range' assert. I attached an example to demonstrate the problem. You can find the code fragment that causes the crash in qtreeview.cpp line 1381 - QTreeViewPrivate::adjustViewOptionsForIndex.

The vector viewItems only contains one object - which i guess is correct, because the first item is hidden - and the model indexes row is 1 - which is also correct. But since the item is accessed with the row of the model index ((viewItems.at(row)), the program crashes.