[gegl] operations: fix npd implementation

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 932e8e543361b073cb54f239ff105818b96cae9b
Author: zamfofex <zamfofex twdb moe>
Date:   Wed Jan 12 00:15:37 2022 -0300

    operations: fix npd implementation

 operations/external/npd.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/operations/external/npd.c b/operations/external/npd.c
index c4cc7843f..e422aba26 100644
--- a/operations/external/npd.c
+++ b/operations/external/npd.c
@@ -178,7 +178,6 @@ process (GeglOperation       *operation,
                                        0, 0, o->square_size);
         }
 
-      model->reference_image = input_image;
       model->display = display;
       props->first_run = FALSE;
     }
@@ -187,6 +186,9 @@ process (GeglOperation       *operation,
     {
       display = model->display;
 
+      display->image.gegl_buffer = output;
+      model->reference_image->gegl_buffer = input;
+
       npd_set_deformation_type (model, o->asap_deformation, o->mls_weights);
 
       if (o->mls_weights &&