Fix QListView assert when the last row is moved in IconMode

After the last row is moved, 0 will be returned when obtaining
row and column data. At this time, QListView::doitemslayout will
not call d->doitemslayout, so the QBspTree data structure will
not be cleaned up, leaving a stale tree structure behind. This
will trigger an assert during paintEvent handling if QListView is
set to IconMode

In QListView::ListMode the test for a valid model index doesn't
use an assert.

Call QListViewPrivate::clear explicitly if the column count is 0
so that the QBspTree and other data structures are cleared.

Add a test case that simulates this scenario by implementing a
model that returns a 0 column count for an index after the model
structure was changed through a move of rows.

Done-with: Volker Hilsheimer
Fixes: QTBUG-95463
Pick-to: 5.15 6.1 6.2
Change-Id: I36419be5459b8ced930c619f538482ea1db4ad03
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

0 files changed, 0 insertions, 0 deletions