[gimp] app: allow calling gimp_tile_handler_validate_validate() with a NULL rect

[Ell <ell src gnome org>]

commit ba6040bbcd940f693fbc1031fe4a5a29466aa883
Author: Ell <ell_se yahoo com>
Date:   Wed Jan 15 21:38:10 2020 +0200

    app: allow calling gimp_tile_handler_validate_validate() with a NULL rect
    
    ... and validate the entire buffer.

 app/gegl/gimptilehandlervalidate.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/app/gegl/gimptilehandlervalidate.c b/app/gegl/gimptilehandlervalidate.c
index f7b24c0c6f..4dde27091d 100644
--- a/app/gegl/gimptilehandlervalidate.c
+++ b/app/gegl/gimptilehandlervalidate.c
@@ -511,6 +511,9 @@ gimp_tile_handler_validate_validate (GimpTileHandlerValidate *validate,
 
   klass = GIMP_TILE_HANDLER_VALIDATE_GET_CLASS (validate);
 
+  if (! rect)
+    rect = gegl_buffer_get_extent (buffer);
+
   if (intersect)
     {
       cairo_region_t *region = cairo_region_copy (validate->dirty_region);