[gegl] raw-load: avoid warning instances of g_clear_pointer

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

commit b96b515c8c12590a5aa4c332ea64bdae49de9387
Author: Øyvind Kolås <pippin gimp org>
Date:   Mon Sep 24 15:01:49 2018 +0200

    raw-load: avoid warning instances of g_clear_pointer

 operations/external/raw-load.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/operations/external/raw-load.c b/operations/external/raw-load.c
index 4b942c8a6..13eb661c2 100644
--- a/operations/external/raw-load.c
+++ b/operations/external/raw-load.c
@@ -80,8 +80,12 @@ raw_close (GeglProperties *o)
   Private *p = (Private*)o->user_data;
 
   g_clear_pointer (&p->cached_path, g_free);
-  g_clear_pointer (&p->image, (GDestroyNotify) libraw_dcraw_clear_mem);
-  g_clear_pointer (&p->LibRaw, (GDestroyNotify) libraw_close);
+  if (p->image)
+    libraw_dcraw_clear_mem (p->image);
+  if (p->LibRaw)
+    libraw_close (p->LibRaw);
+  p->image = NULL;
+  p->LibRaw = NULL;
 }
 
 static void