x11-tfp: don't call winsys x11_damage_notify without winsys
x11-tfp: don't call winsys x11_damage_notify without winsys

If we failed to create a native texture from pixmap via EGL or GLX then
we shouldn't call the winsys's texture_pixmap_x11_damage_notify
function. By doing the validation in cogl-texture-pixmap-x11.c the
winsys code can continue to assume that it doesn't need to verify there
is a valid tex_pixmap->winsys pointer.

Thanks to Damien Leone <dleone@nvidia.com> for catching this issue.

https://bugzilla.gnome.org/show_bug.cgi?id=660184

Distrotech/cogl,collects/cogl,gcampax/cogl,djdeath/cogl,gcampax/cogl,djdeath/cogl-android,Distrotech/cogl,djdeath/cogl-android,djdeath/cogl,collects/cogl,djdeath/cogl-android,Distrotech/cogl,gcampax/cogl,djdeath/cogl,Distrotech/cogl,gcampax/cogl