[gimp] app: in bucket fill tool, don't calculate line art of layer groups

[Ell <ell src gnome org>]

commit 4b4fffbd0e21f0682ec9e39ab6ed40913513f3f9
Author: Ell <ell_se yahoo com>
Date:   Mon Jan 7 04:22:43 2019 -0500

    app: in bucket fill tool, don't calculate line art of layer groups
    
    ... since they can't be used with the fill tool.

 app/tools/gimpbucketfilltool.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/app/tools/gimpbucketfilltool.c b/app/tools/gimpbucketfilltool.c
index 16be37ea3c..7d9f83006c 100644
--- a/app/tools/gimpbucketfilltool.c
+++ b/app/tools/gimpbucketfilltool.c
@@ -847,6 +847,9 @@ gimp_bucket_fill_tool_reset_line_art (GimpBucketFillTool    *tool,
     {
       GimpDrawable *drawable = gimp_image_get_active_drawable (image);
 
+      if (gimp_viewable_get_children (GIMP_VIEWABLE (drawable)))
+        drawable = NULL;
+
       if (options->sample_merged)
         gimp_line_art_set_input (line_art, GIMP_PICKABLE (image));
       else if (drawable)