BUG/MINOR: fix unterminated ACL array in compression

Recent commit 727db8b4 was lacking a NULL ACL descriptor to terminate
the array, causing a random behaviour upon startup. No backport is needed.
diff --git a/src/compression.c b/src/compression.c
index e75f21e..906e4fd 100644
--- a/src/compression.c
+++ b/src/compression.c
@@ -637,6 +637,7 @@
 /* Note: must not be declared <const> as its list will be overwritten */
 static struct acl_kw_list acl_kws = {{ },{
 	{ "res.comp",          NULL,            acl_parse_nothing,     acl_match_nothing  },
+	{ /* END */ },
 }};
 
 /* Note: must not be declared <const> as its list will be overwritten */