[gegl] matting-global: opt out of auto threading

[Thomas Manni <tmanni src gnome org>]

commit c3b107d002ff20d11f256cefb232aa9b1c9d0725
Author: Thomas Manni <thomas manni free fr>
Date:   Sat Jul 20 16:46:36 2019 +0200

    matting-global: opt out of auto threading
    
    Fix issue https://gitlab.gnome.org/GNOME/gimp/issues/3671

 operations/common/matting-global.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/operations/common/matting-global.c b/operations/common/matting-global.c
index 677791f60..376ee9e51 100644
--- a/operations/common/matting-global.c
+++ b/operations/common/matting-global.c
@@ -484,6 +484,7 @@ static void gegl_op_class_init (GeglOpClass *klass)
   operation_class->prepare                 = matting_prepare;
   operation_class->get_required_for_output = matting_get_required_for_output;
   operation_class->get_cached_region       = matting_get_cached_region;
+  operation_class->threaded                = FALSE;
 
   gegl_operation_class_set_keys (operation_class,
     "name"       , "gegl:matting-global",