BUG: Fixed crash in Transform widget

When hardened transform or untransformed multiple transformed items (with multi-select) then Slicer crashed.
Applied the same fix as in http://www.na-mic.org/Bug/view.php?id=2578.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22615 3bd1e089-480b-0410-8dfb-8563597acbee