Calling QColumnView::setCurrentIndex() can delete columns from the view

After http://codereview.qt-project.org/#change,8644 (which change QTest::qWait to process all DeferredDelete events), the tst_QColumnView::parentCurrentIndex() test function crashes on the last statement of the test function. This crash seems to occur because the last call to view.setCurrentIndex() sets up a deferred delete of the last column of the view. I am not aware of any valid reason for setting the current index to cause any part of a view to be deleted.