[gimp] Add separate check that prevents merging down to a group layer

[Michael Natterer <mitch src gnome org>]

commit eb03413b49d81436082a7ae97fa94849b205cc1d
Author: Michael Natterer <mitch gimp org>
Date:   Sat Aug 29 12:26:15 2009 +0200

    Add separate check that prevents merging down to a group layer

 app/core/gimpimage-merge.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/app/core/gimpimage-merge.c b/app/core/gimpimage-merge.c
index 2d06c22..609c64a 100644
--- a/app/core/gimpimage-merge.c
+++ b/app/core/gimpimage-merge.c
@@ -216,6 +216,13 @@ gimp_image_merge_down (GimpImage      *image,
 
       if (gimp_item_get_visible (GIMP_ITEM (layer)))
         {
+          if (gimp_viewable_get_children (GIMP_VIEWABLE (layer)))
+            {
+              g_set_error_literal (error, 0, 0,
+                                   _("Cannot merge down to a group layer."));
+              return NULL;
+            }
+
           if (gimp_item_get_lock_content (GIMP_ITEM (layer)))
             {
               g_set_error_literal (error, 0, 0,