object-file: fix indent-with-space

Commit b25562e63f (object-file: inline calls to read_object(),
2023-01-07) accidentally indented a conditional block with spaces
instead of a tab.

Reported-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Acked-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

object-file.c

@@ -1708,7 +1708,7 @@ void *repo_read_object_file(struct repository *r,
 	oi.sizep = size;
 	oi.contentp = &data;
 	if (oid_object_info_extended(r, oid, &oi, flags))
-	    return NULL;
+		return NULL;
 
 	return data;
 }