Fix segfault if no arg has been specified, there is still some other issue…

Fix segfault if no arg has been specified, there is still some other issue lurking in the code though

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@8327 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/mod/languages/mod_lua/freeswitch_lua.cpp

@@ -130,7 +130,9 @@ void Session::setHangupHook(char *func, char *arg) {
 	
 	if (func) {
 		hangup_func_str = strdup(func);
-		hangup_func_arg = strdup(arg);
+		if (arg) {
+			hangup_func_arg = strdup(arg);
+		}
 		switch_channel_set_private(channel, "CoreSession", this);
 		hook_state = switch_channel_get_state(channel);
 		switch_core_event_hook_add_state_change(session, lua_hanguphook);