Surface::currentSurfaceBuffer can be 0
Surface::currentSurfaceBuffer can be 0

Change-Id: I107f74dbabb5d8192d44f3f76dc38852928847b9
Reviewed-by: Laszlo Agocs <00c05606d635b5d8e1450a8536e4e2809abe4e80@digia.com>

locusf/qtwayland-1,locusf/qtwayland-1,locusf/qtwayland-1,Tofee/qtwayland,locusf/qtwayland-1,ntanibata/qtwayland,Tofee/qtwayland,ntanibata/qtwayland,Tofee/qtwayland,ntanibata/qtwayland