commit-graph: fix start_delayed_progress() leak

In commit-graph.c:graph_write(), if read_one_commit() failed,
progress allocated in start_delayed_progress() will leak. Add
stop_progress() before goto cleanup.

Signed-off-by: Lidong Yan <502024330056@smail.nju.edu.cn>
Acked-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/commit-graph.c

@@ -311,6 +311,7 @@ static int graph_write(int argc, const char **argv, const char *prefix,
 		while (strbuf_getline(&buf, stdin) != EOF) {
 			if (read_one_commit(&commits, progress, buf.buf)) {
 				result = 1;
+				stop_progress(&progress);
 				goto cleanup;
 			}
 		}