st: Keep weak ref on texture cache bound texture source
We don't keep any ref on it, so it might leave us with a dangling pointer here. Fixes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3491 Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1672> (cherry picked from commit 87558efb)
parent
296e76d2