[gimp] app: fix a crash in bucket fill tool.

[Jehan <jehanp src gnome org>]

commit 0a952a3429b01223d7db5ccdbdb2fef0235bb516
Author: Jehan <jehan girinstud io>
Date:   Thu Jan 17 13:48:40 2019 +0100

    app: fix a crash in bucket fill tool.
    
    In commit c71b4916af, I forgot to disconnect signals on the bucket fill
    options at finalization, leading the software to crash on an
    non-existing tool.

 app/tools/gimpbucketfilltool.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/app/tools/gimpbucketfilltool.c b/app/tools/gimpbucketfilltool.c
index 49edb1f625..6f62d4da70 100644
--- a/app/tools/gimpbucketfilltool.c
+++ b/app/tools/gimpbucketfilltool.c
@@ -258,6 +258,7 @@ gimp_bucket_fill_tool_finalize (GObject *object)
     }
   g_clear_object (&tool->priv->line_art);
 
+  g_signal_handlers_disconnect_by_data (options, tool);
   g_signal_handlers_disconnect_by_data (context, tool);
 
   G_OBJECT_CLASS (parent_class)->finalize (object);