[gnome-disk-utility] Fix a null dereference

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 034f435b395e87126f420b510bf3077711b23eb1
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Mar 17 14:56:40 2017 -0400

    Fix a null dereference
    
    Coverity is flagging this.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=780218

 src/disks/gduwindow.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/disks/gduwindow.c b/src/disks/gduwindow.c
index a3682fd..b8f2d8e 100644
--- a/src/disks/gduwindow.c
+++ b/src/disks/gduwindow.c
@@ -797,7 +797,7 @@ init_css (GduWindow *window)
   provider = gtk_css_provider_new ();
   file = g_file_new_for_uri ("resource:///org/gnome/Disks/ui/gdu.css");
   error = NULL;
-  if (!gtk_css_provider_load_from_file (provider, file, NULL))
+  if (!gtk_css_provider_load_from_file (provider, file, &error))
     {
       g_warning ("Can’t parse custom CSS: %s\n", error->message);
       g_error_free (error);