Tread more carefull when printing debug output during refcount_release (prevent segfault (&obj_info[obj->type])->debugcat, which can happens when multiple releases coincide (sccp_event release for example))

git-svn-id: https://svn.code.sf.net/p/chan-sccp-b/code/trunk@5154 43c1dc8c-776e-4df2-8ef1-6e829299be21