This makes it possible for uic to handle QTreeWidget that in
the designer has one or more empty headers.
Before the right(most) empty items where there wasn't a
non-empty header to the right of them would not be visible.
The other empty items - where there was a header to the
right of it would not be empty but initialized with a number.
This patch ensures the same behavior that the QTableWidget
is having.
Task-number: QTBUG-18156
Change-Id: I19bfd3307befe46a1af2d6a3275f7446a15b3442
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
