debian: don't fail the upgrade if glib-compile-schemas fails

Thanks @adrelanos

debian/qubes-core-agent.postinst

@@ -141,7 +141,7 @@ case "${1}" in
             dpkg-statoverride --update --add user user 775 /var/lib/qubes/dom0-updates
         fi
 
-        glib-compile-schemas /usr/share/glib-2.0/schemas
+        glib-compile-schemas /usr/share/glib-2.0/schemas || true
 
 
         # Update Qubes App Menus