crash in model/view framework

Sequence of steps to reproduce crash:

1)Create tree similar to

 
root
 |-- ch1
 |    |-- n1
 |
 |-- ch2
      |- n2

2)Filter out ch1 and ch2 with QSortFilterProxyModel::filterAcceptsRow

3) Try to remove 1st and 2nd rows (ch1 and ch2)

4) CRASH!

My initial investigation and gdb say that in function

void QSortFilterProxyModelPrivate::updateChildrenMapping(const QModelIndex &source_parent, Mapping *parent_mapping,
                                                         Qt::Orientation orient, int start, int end, int delta_item_count, bool remove)

at line

            Mapping *cm = source_index_mapping.take(source_child_index);

you get null cm, because hash source_index_mapping does not contain such source_child_index index and then you are trying to use it.

In attachment is minimal example to reproduce the bug.

P.S. Yes, I know that I can say to function removeRows to remove two rows at once, but this example was taken from real big programme, and in this real programme it is difficult and not efficiently to combine separate rows in one bundle.