Add name_lookup function in object_ops.

diff --git a/server/mapping.c b/server/mapping.c
index 2825ef6..62d98c1 100644
--- a/server/mapping.c
+++ b/server/mapping.c
@@ -63,6 +63,7 @@
     NULL,                        /* satisfied */
     no_signal,                   /* signal */
     mapping_get_fd,              /* get_fd */
+    no_lookup_name,              /* lookup_name */
     no_close_handle,             /* close_handle */
     mapping_destroy              /* destroy */
 };