Commit ec9b6c314dc018bbf0af4ff657fa5ff56a5bf9f7 breaks existing programs

[Nikolaus Waxweiler]

Hi!
Not sure if this is intentional or anything, but the aforementioned 
commit makes programs fail to render on Fedora 33. I.e. GTK3 apps spam 
the console with

(gnome-calculator:44487): Gtk-WARNING **: 23:32:19.658: drawing failure 
for widget 'MathWindow': invalid value for an input cairo_format_t

and don't render any UI. Can't run git master anymore :(