am: release strbuf after use in safe_to_abort()

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/am.c b/builtin/am.c
index 3d38b3f..d7513f5 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -2105,6 +2105,7 @@ static int safe_to_abort(const struct am_state *state)
 			die(_("could not parse %s"), am_path(state, "abort-safety"));
 	} else
 		oidclr(&abort_safety);
+	strbuf_release(&sb);
 
 	if (get_oid("HEAD", &head))
 		oidclr(&head);