QTreeView: drag and drop onto an item causes the item to become unresponsive to expand/collapse requests for several seconds after a drop onto that item

Using the attached example it should be observed that after dragging an item (file) from one folder to another (that's in the collapsed state), that the target folder cannot be expanded until several seconds after the drop.

This was tested using 4.6.1/4.6.2/4.6.3 and 4.7-rc1 on Windows 7.