X11: Fix crash in gdk_x11_gl_context_texture_from_surface
X11: Fix crash in gdk_x11_gl_context_texture_from_surface

We need to look at the impl_window for the gl rendering, not
the subwindow we're rendering into.

jadahl/gtk,jigpu/gtk,chergert/gtk,ahodesuka/gtk,Lyude/gtk-,jigpu/gtk,alexlarsson/gtk,Lyude/gtk-,jadahl/gtk,jadahl/gtk,grubersjoe/adwaita,Lyude/gtk-,chergert/gtk,jigpu/gtk,ahodesuka/gtk,Adamovskiy/gtk,Adamovskiy/gtk,ahodesuka/gtk,grubersjoe/adwaita,ahodesuka/gtk,alexlarsson/gtk,Lyude/gtk-,alexlarsson/gtk,ahodesuka/gtk,jadahl/gtk,grubersjoe/adwaita,ahodesuka/gtk,chergert/gtk,davidgumberg/gtk,ahodesuka/gtk,chergert/gtk,alexlarsson/gtk,alexlarsson/gtk,jigpu/gtk,Adamovskiy/gtk,chergert/gtk,alexlarsson/gtk,grubersjoe/adwaita,alexlarsson/gtk,Adamovskiy/gtk,Adamovskiy/gtk,davidgumberg/gtk,Lyude/gtk-,jadahl/gtk,davidgumberg/gtk,Adamovskiy/gtk,grubersjoe/adwaita,jigpu/gtk,chergert/gtk,jigpu/gtk,Lyude/gtk-,jigpu/gtk,davidgumberg/gtk,jadahl/gtk,grubersjoe/adwaita,Lyude/gtk-,davidgumberg/gtk,alexlarsson/gtk,chergert/gtk,grubersjoe/adwaita,Adamovskiy/gtk,Lyude/gtk-,jigpu/gtk,Adamovskiy/gtk,chergert/gtk,jadahl/gtk,ahodesuka/gtk,davidgumberg/gtk,davidgumberg/gtk,jadahl/gtk,davidgumberg/gtk,grubersjoe/adwaita