[gimp] plug-ins: fix usage of gimp_file_save() in py-slice.py.

[Jehan <jehanp src gnome org>]

commit 30e7be6db1032f16c8dd5b9901dc67eb06860ad8
Author: Jehan <jehan girinstud io>
Date:   Sat Oct 12 13:55:07 2019 +0200

    plug-ins: fix usage of gimp_file_save() in py-slice.py.
    
    Signature changed (commit f3fb3d1a), but build could not catch the
    missing usage in non-compiled scripts. Thanks to Massimo for noticing
    it.

 plug-ins/python/py-slice.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/plug-ins/python/py-slice.py b/plug-ins/python/py-slice.py
index c92308a294..01df236a5a 100755
--- a/plug-ins/python/py-slice.py
+++ b/plug-ins/python/py-slice.py
@@ -196,7 +196,8 @@ def slice(image, drawable, image_path, image_basename, image_extension,
     if image_extension == "jpg" and image.base_type() == Gimp.ImageBaseType.INDEXED:
         temp_image.convert_rgb ()
 
-    Gimp.file_save(Gimp.RunMode.NONINTERACTIVE, temp_image, temp_drawable, filename, filename)
+    Gimp.file_save(Gimp.RunMode.NONINTERACTIVE, temp_image, temp_drawable,
+                   Gio.file_new_for_path (filename))
 
     temp_image.delete()
     return src