[frogr] Added missing null check

[Mario Sanchez Prada <msanchez src gnome org>]

commit 8956cf7ba7726bd8629f5f20d2a6fd063ba43eff
Author: Mario Sanchez Prada <msanchez gnome org>
Date:   Fri Nov 2 09:06:19 2012 +0100

    Added missing null check

 src/frogr-controller.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/frogr-controller.c b/src/frogr-controller.c
index e20189e..85ba84a 100644
--- a/src/frogr-controller.c
+++ b/src/frogr-controller.c
@@ -273,7 +273,8 @@ _clear_cancellable (FrogrController *self)
   FrogrControllerPrivate *priv = NULL;
 
   priv = FROGR_CONTROLLER_GET_PRIVATE (self);
-  g_object_unref (priv->cancellable);
+  if (priv->cancellable)
+    g_object_unref (priv->cancellable);
 
   priv->cancellable = NULL;
 }