[gimp] app: in GimpLineArt, ref input pickable

[Ell <ell src gnome org>]

commit c8b5c81a418ab8e4997dc5bbffaa5a671d479e20
Author: Ell <ell_se yahoo com>
Date:   Mon Nov 4 12:51:09 2019 +0200

    app: in GimpLineArt, ref input pickable
    
    ... in particular, so that the GimpLineArt object can take
    ownership over newly-created GimpImageProxy inputs.

 app/core/gimplineart.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/app/core/gimplineart.c b/app/core/gimplineart.c
index 758426c3f3..04b71a1a30 100644
--- a/app/core/gimplineart.c
+++ b/app/core/gimplineart.c
@@ -497,7 +497,7 @@ gimp_line_art_set_input (GimpLineArt  *line_art,
       if (line_art->priv->input)
         g_signal_handlers_disconnect_by_data (line_art->priv->input, line_art);
 
-      line_art->priv->input = pickable;
+      g_set_object (&line_art->priv->input, pickable);
 
       gimp_line_art_compute (line_art);