Initialize count to 0 in wl_list_length().

Not sure how this ever really worked before...

wayland-util.c

@@ -121,6 +121,7 @@ wl_list_length(struct wl_list *list)
 	struct wl_list *e;
 	int count;
 
+	count = 0;
 	e = list->next;
 	while (e != list) {
 		e = e->next;