Avoid undefined color values in corrupt xpm image
Issue reported by Codechecker.
Pick-to: 6.1 6.0 5.15 5.12 Change-Id: I1a5aa2203fb31e0ce3b630a11e450925aee81fb0 Reviewed-by: Allan Sandfeld Jensen allan.jensen@qt.io (cherry picked from commit f651e6a2)