[gnome-desktop] gnome-bg: Add some check to avoid weird crash

[Vincent Untz <vuntz src gnome org>]

commit b081283225167b56d4df9aff7631075f9f57747a
Author: Gordon Allott <gord allott canonical com>
Date:   Mon Feb 13 19:16:04 2012 +0100

    gnome-bg: Add some check to avoid weird crash
    
    https://bugzilla.gnome.org/show_bug.cgi?id=670000

 libgnome-desktop/gnome-bg.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/libgnome-desktop/gnome-bg.c b/libgnome-desktop/gnome-bg.c
index ca7f1d2..0357c71 100644
--- a/libgnome-desktop/gnome-bg.c
+++ b/libgnome-desktop/gnome-bg.c
@@ -305,7 +305,7 @@ gnome_bg_load_from_preferences (GnomeBG   *bg,
 	/* Filename */
 	filename = NULL;
 	tmp = g_settings_get_string (settings, BG_KEY_PICTURE_URI);
-	if (*tmp != '\0') {
+	if (tmp && *tmp != '\0') {
 		filename = g_filename_from_uri (tmp, NULL, NULL);
 		if (filename != NULL && g_file_test (filename, G_FILE_TEST_EXISTS) == FALSE) {
 			g_free (filename);