QtAbstractItemModel asserts when being rapidly modified

Tested with the in-progress example from QTBUG-125976.

Steps:

1. Add 20 rows and 20 columns to the model
2. Remove column/row
3. Add column/row
4. Loop step 2 & 3 for a few clicks.

Result:
After some rows and columns, adding new ones becomes noticeably laggy.
After 1-10 loops of steps 2 & 3, the application hits an assert and shuts down.

Log: log.txt