[gtk] x11: Avoid a division by zero

[Debarshi Ray <debarshir src gnome org>]

commit 01fda3b85ee383637fb9d4befb1bfb7e5cae93b1
Author: Pavel Roskin <plroskin gmail com>
Date:   Thu Mar 8 15:58:42 2018 +0100

    x11: Avoid a division by zero
    
    This is similar to f44baf51d9e8616a but for RandR 1.3 servers like
    x11rdp and Windows Exceed which don't return a refresh rate. Avoid a
    crash when that happens.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=775546

 gdk/x11/gdkscreen-x11.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/gdk/x11/gdkscreen-x11.c b/gdk/x11/gdkscreen-x11.c
index 2d973d425b..2ca0ac7886 100644
--- a/gdk/x11/gdkscreen-x11.c
+++ b/gdk/x11/gdkscreen-x11.c
@@ -548,7 +548,8 @@ init_randr13 (GdkX11Screen *x11_screen, gboolean *changed)
               XRRModeInfo *xmode = &resources->modes[j];
               if (xmode->id == crtc->mode)
                 {
-                  refresh_rate = (1000 * xmode->dotClock) / (xmode->hTotal *xmode->vTotal);
+                  if (xmode->hTotal != 0 && xmode->vTotal != 0)
+                    refresh_rate = (1000 * xmode->dotClock) / (xmode->hTotal * xmode->vTotal);
                   break;
                 }
             }