basesrc: do not leak buffer pool in error case

https://bugzilla.gnome.org/show_bug.cgi?id=747321

libs/gst/base/gstbasesrc.c

@@ -3115,6 +3115,7 @@ config_failed:
   GST_ELEMENT_ERROR (basesrc, RESOURCE, SETTINGS,
       ("Failed to configure the buffer pool"),
       ("Configuration is most likely invalid, please report this issue."));
+  gst_object_unref (pool);
   return FALSE;
 }