ref-filter.c: fix a leak in get_head_description

In 2708ce6 (branch: sort detached HEAD based on a flag, 2021-01-07) a
call to wt_status_state_free_buffers, responsible of freeing the
resources that could be allocated in the local struct wt_status_state
state, was eliminated.

The call to wt_status_state_free_buffers was introduced in 962dd7e
(wt-status: introduce wt_status_state_free_buffers(), 2020-09-27).  This
commit brings back that call in get_head_description.

Signed-off-by: Rubén Justo <[email protected]>
Reviewed-by: Martin Ågren <[email protected]>
Acked-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: rjusto

ref-filter.c

@@ -1571,6 +1571,8 @@ char *get_head_description(void)
 	} else
 		strbuf_addstr(&desc, _("(no branch)"));
 
+	wt_status_state_free_buffers(&state);
+
 	return strbuf_detach(&desc, NULL);
 }