more const madness

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@11355 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/switch_event.c

@@ -1251,7 +1251,7 @@ SWITCH_DECLARE(char *) switch_event_expand_headers(switch_event_t *event, const
 	char *func_val = NULL;
 	int nv = 0;
 
-	nv = switch_string_var_check((char *)in, SWITCH_FALSE);
+	nv = switch_string_var_check_const(in);
 
 	if (!nv) {
 		return (char *) in;