[gthumb] desktop background: fixed error when setting an xcf image as background

[Paolo Bacchilega <paobac src gnome org>]

commit ffade3f53ea1dcdb034ff8768794867172d922e0
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Thu Jan 12 11:26:35 2017 +0100

    desktop background: fixed error when setting an xcf image as background

 extensions/desktop_background/actions.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/extensions/desktop_background/actions.c b/extensions/desktop_background/actions.c
index af7a227..642bb8f 100644
--- a/extensions/desktop_background/actions.c
+++ b/extensions/desktop_background/actions.c
@@ -391,7 +391,10 @@ gth_browser_activate_set_desktop_background (GSimpleAction *action,
                        GthImage *image;
                        GthTask  *task;
 
-                       image = gth_image_new_for_surface (gth_image_viewer_page_get_modified_image 
(GTH_IMAGE_VIEWER_PAGE (viewer_page)));
+                       if (gth_image_viewer_page_get_is_modified (GTH_IMAGE_VIEWER_PAGE (viewer_page)))
+                               image = gth_image_new_for_surface (gth_image_viewer_page_get_modified_image 
(GTH_IMAGE_VIEWER_PAGE (viewer_page)));
+                       else
+                               image = gth_image_new_for_surface (gth_image_viewer_page_get_current_image 
(GTH_IMAGE_VIEWER_PAGE (viewer_page)));
                        file_data = gth_file_data_new (wdata->new_style.file, NULL);
                        task = gth_save_image_task_new (image,
                                                        "image/jpeg",