 Don't try to draw shader effect sources with dims < 0.
 Don't try to draw shader effect sources with dims < 0.

Task-number: QTBUG-40099
Change-Id: I0eb0d877963a9394765ec8e0f10569a98a263743
Reviewed-by: Simon Hausmann <a975102812d593b3191088e3d0aeaeb6f11dbcf5@digia.com>

mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d,mgrunditz/qtdeclarative-2d