[gegl] operations: buffer sampler was not properly freed.

[Jehan <jehanp src gnome org>]

commit c5317a7ed3cfcac4540273fb6bd4dda9c92260c8
Author: Jehan <jehan girinstud io>
Date:   Mon Nov 5 11:18:12 2018 +0100

    operations: buffer sampler was not properly freed.

 operations/common/watershed-transform.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/operations/common/watershed-transform.c b/operations/common/watershed-transform.c
index 5da36f118..869e57b2b 100644
--- a/operations/common/watershed-transform.c
+++ b/operations/common/watershed-transform.c
@@ -415,6 +415,7 @@ process (GeglOperation       *operation,
 
       g_free (p);
     }
+  g_object_unref (gradient_sampler);
 
   HQ_clean (&hq);
   return  TRUE;