[gnome-desktop] gnome_bg_slide_show_get_current_slide: add NULL check

[Michael Catanzaro <mcatanzaro src gnome org>]

commit d35c6e0e41ec8c0426d1317b9f28f485b7b4530d
Author: Mike Gorse <mgorse suse com>
Date:   Wed Sep 16 15:02:30 2020 -0500

    gnome_bg_slide_show_get_current_slide: add NULL check
    
    Ensure that a file is present. Guards against a crash in case of a
    malformed xml file.
    
        Resolves: https://gitlab.gnome.org/GNOME/gnome-desktop/-/issues/169

 libgnome-desktop/gnome-bg-slide-show.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/libgnome-desktop/gnome-bg-slide-show.c b/libgnome-desktop/gnome-bg-slide-show.c
index cad3cb6c..760ed566 100644
--- a/libgnome-desktop/gnome-bg-slide-show.c
+++ b/libgnome-desktop/gnome-bg-slide-show.c
@@ -543,7 +543,7 @@ gnome_bg_slide_show_get_current_slide (GnomeBGSlideShow  *self,
                         if (is_fixed)
                             *is_fixed = slide->fixed;
 
-                        if (file1)
+                        if (file1 && slide->file1)
                             *file1 = find_best_size (slide->file1, width, height);
 
                         if (file2 && slide->file2)