xfree86/modes: Bail from xf86RotateRedisplay if pScreen->root is NULL
Avoids a crash in xf86RotatePrepare -> DamageRegister during CreateScreenResources if rotation or another transform is configured for any connected RandR output in xorg.conf. The generic rotation/transform code generally can't work without the root window currently. Closes: xorg/xserver#969 Fixes: 094f42cd "xfree86/modes: Call xf86RotateRedisplay from xf86CrtcRotate" Acked-by: Olivier Fourdan <ofourdan@redhat.com> Reviewed-by: Adam Jackson <ajax@redhat.com>