[gnome-control-center/wip/jsparber/background] background: fix build warning: set slideshow_emblem to NULL

[Julian Sparber <jsparber src gnome org>]

commit df1e500180f8970722ae9b36f4d7909a0adbcb92
Author: Julian Sparber <julian sparber net>
Date:   Tue Feb 6 23:17:53 2018 +0100

    background: fix build warning: set slideshow_emblem to NULL
    
    https://bugzilla.gnome.org/show_bug.cgi?id=788515

 panels/background/cc-background-grid-item.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/panels/background/cc-background-grid-item.c b/panels/background/cc-background-grid-item.c
index e219ed3..e6c1000 100644
--- a/panels/background/cc-background-grid-item.c
+++ b/panels/background/cc-background-grid-item.c
@@ -49,7 +49,7 @@ static GdkPixbuf *
 load_slideshow_emblem (CcBackgroundGridItem *item,
                        gint                  scale_factor)
 {
-  GdkPixbuf *slideshow_emblem;
+  GdkPixbuf *slideshow_emblem = NULL;
   GIcon *icon = NULL;
   GtkIconInfo *icon_info = NULL;
   GError *error = NULL;