Assert when dragging an index that is not in the first column

Following assert failure occurs in QTreeView when dragging an index that is not in the first column:

ASSERT failure in QVector<T>::at: "index out of range", file qt_path\include\qtcore\../../src/corelib/tools/qvector.h, line 332

Issue can be seen with the attached project of a QTreeView which has a root-item and images as childs in one row. The error occurs when trying repeatedly to start a drag on a picture, except for column 1. It doesn't always get hit because it depends on what area was last painted.

This error can be reproduced at least on Win 7 32bit (Qt 4.8.0 and 4.8.1) and 64bit (4.8.1). On Qt 4.7. everything works fine. Result of a bisect was that this huge merge broke the functionality:
http://qt.gitorious.org/qt/qt/commit/939c66a788c5ab3bbd630732f5c85c50bb80ce1a/diffs