Proxy Source Mapping Issue

Attached is a repro case that generates the assert 

 The example is a modified version of this:

https://github.com/scopchanov/SO-CustomList

The modified version consists these class

   QSortFilterProxyModel 

   QListView to display the proxy

  QStyledItemDelegate for painting

  QStandardItemModel for the items

  QStandardItem items

When you hit the space key, an item is inserted into a random row.

To reproduce the issue, scroll to the bottom and hit the space key. This should generate the assert.

There is no assert if the space key is hit when displaying the top of the item list.

 The insert code is in the keyPressEvent function in ListView.cpp