[gimp] libgimpwidgets: don't unref a NULL transforms from the transform cache

[Michael Natterer <mitch src gnome org>]

commit 70463a74fa09cdd15a2ac0926b95335f44648fd6
Author: Michael Natterer <mitch gimp org>
Date:   Mon May 30 12:48:10 2016 +0200

    libgimpwidgets: don't unref a NULL transforms from the transform cache

 libgimpwidgets/gimpwidgetsutils.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/libgimpwidgets/gimpwidgetsutils.c b/libgimpwidgets/gimpwidgetsutils.c
index 0f5e4e4..fd636f0 100644
--- a/libgimpwidgets/gimpwidgetsutils.c
+++ b/libgimpwidgets/gimpwidgetsutils.c
@@ -547,7 +547,9 @@ transform_cache_config_notify (GObject          *config,
 
   g_signal_handler_disconnect (config, cache->notify_id);
 
-  g_object_unref (cache->transform);
+  if (cache->transform)
+    g_object_unref (cache->transform);
+
   g_object_unref (cache->src_profile);
   g_object_unref (cache->dest_profile);