[libwnck/wip/muktupavels/issue-154: 4/4] xutils: check if XRes is available before using XResQueryClientIds

[Alberts Muktupāvels <muktupavels src gnome org>]

commit dde756bc7788488f07b674cbe218943a62eb82e6
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Fri Sep 30 18:43:07 2022 +0300

    xutils: check if XRes is available before using XResQueryClientIds
    
    https://gitlab.gnome.org/GNOME/libwnck/-/issues/154

 libwnck/xutils.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/libwnck/xutils.c b/libwnck/xutils.c
index 08be8aa9..91c2d50e 100644
--- a/libwnck/xutils.c
+++ b/libwnck/xutils.c
@@ -1156,6 +1156,9 @@ xres_get_pid (WnckScreen *screen,
   long client_id_count = 0;
   XResClientIdValue *client_ids = NULL;
 
+  if (!_wnck_handle_has_xres (wnck_screen_get_handle (screen)))
+    return -1;
+
   xscreen = _wnck_screen_get_xscreen (screen);
 
   client_spec.client = xwindow;