[mutter] screen: Crash when we can't load a cursor

[Jasper St. Pierre <jstpierre src gnome org>]

commit 5ad15bb5e5ff1905167a7ea133c26399e060114b
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Sun Dec 28 22:13:44 2014 -0800

    screen: Crash when we can't load a cursor
    
    To make it easier for users to understand why their cursor disappeared.

 src/core/screen.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/src/core/screen.c b/src/core/screen.c
index 13e8c7f..6121724 100644
--- a/src/core/screen.c
+++ b/src/core/screen.c
@@ -1262,9 +1262,11 @@ meta_screen_update_cursor (MetaScreen *screen)
   MetaCursorTracker *tracker = meta_cursor_tracker_get_for_screen (screen);
 
   cursor_ref = meta_cursor_reference_from_theme (cursor);
+  if (cursor_ref == NULL)
+    g_fatal ("Could not find cursor. Perhaps set XCURSOR_PATH?");
+
   meta_cursor_tracker_set_root_cursor (tracker, cursor_ref);
-  if (cursor_ref)
-    meta_cursor_reference_unref (cursor_ref);
+  meta_cursor_reference_unref (cursor_ref);
 
   /* Set a cursor for X11 applications that don't specify their own */
   xcursor = meta_display_create_x_cursor (display, cursor);