[mutter] cursor-renderer-native: Avoid a crash if we fail to allocate a gbm bo

[Rui Matos <rtcm src gnome org>]

commit 19d814c8876cfc0f9eec78d0cf60d6d6c8e5fb34
Author: Rui Matos <tiagomatos gmail com>
Date:   Fri Jan 8 16:09:10 2016 +0100

    cursor-renderer-native: Avoid a crash if we fail to allocate a gbm bo
    
    https://bugzilla.gnome.org/show_bug.cgi?id=758613

 src/backends/native/meta-cursor-renderer-native.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/backends/native/meta-cursor-renderer-native.c 
b/src/backends/native/meta-cursor-renderer-native.c
index 444154c..297400e 100644
--- a/src/backends/native/meta-cursor-renderer-native.c
+++ b/src/backends/native/meta-cursor-renderer-native.c
@@ -258,6 +258,9 @@ has_valid_cursor_sprite_gbm_bo (MetaCursorSprite *cursor_sprite)
   MetaCursorNativePrivate *cursor_priv =
     g_object_get_qdata (G_OBJECT (cursor_sprite), quark_cursor_sprite);
 
+  if (!cursor_priv)
+    return FALSE;
+
   switch (cursor_priv->pending_bo_state)
     {
     case META_CURSOR_GBM_BO_STATE_NONE: