[mutter/wip/texture-purge-on-nvidia: 29/71] backends/x11: Only free cursor if it was created successfully

[Ray Strode <halfline src gnome org>]

commit bcba6571f05f8b14dd3a5b7fea9e56c5737d487d
Author: Sebastian Keller <sebastian-keller gmx de>
Date:   Thu Aug 2 00:58:56 2018 +0200

    backends/x11: Only free cursor if it was created successfully
    
    XcursorLibraryLoadCursor can return 'None' if the current cursor theme
    is missing the requested icon. If XFreeCursor is then called on this
    cursor, it generates a BadCursor error causing gnome-shell to crash.
    
    Fixes https://gitlab.gnome.org/GNOME/mutter/issues/254
    
    (cherry picked from commit 1bfa20929b36d06cc23667d1122175149615b56d)

 src/core/screen.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/src/core/screen.c b/src/core/screen.c
index 048104150..85a55b1e3 100644
--- a/src/core/screen.c
+++ b/src/core/screen.c
@@ -1397,7 +1397,9 @@ meta_screen_update_cursor (MetaScreen *screen)
 
   XDefineCursor (display->xdisplay, screen->xroot, xcursor);
   XFlush (display->xdisplay);
-  XFreeCursor (display->xdisplay, xcursor);
+
+  if (xcursor)
+    XFreeCursor (display->xdisplay, xcursor);
 }
 
 void