build: fix recent compilation error on GNU/Hurd

* src/copy.c (set_author): Revert change from MACH_PORT_NULL to
MACH_PORT_nullptr from commit 16b5ca6e (2023-06-29).

diff --git a/src/copy.c b/src/copy.c
index 90eebf6bc35c59688191b5ba4b409a9dc0730913..a4aad06a8ec826273a1bb4cfb2530ffefa4d7d31 100644 (file)
--- a/src/copy.c
+++ b/src/copy.c
@@ -981,7 +981,7 @@ set_author (char const *dst_name, int dest_desc, const struct stat *src_sb)
   file_t file = (dest_desc < 0
                  ? file_name_lookup (dst_name, 0, 0)
                  : getdport (dest_desc));
-  if (file == MACH_PORT_nullptr)
+  if (file == MACH_PORT_NULL)
     error (0, errno, _("failed to lookup file %s"), quoteaf (dst_name));
   else
     {