Add name_lookup function in object_ops.

diff --git a/server/mutex.c b/server/mutex.c
index 439af5e..52e6d8cbd 100644
--- a/server/mutex.c
+++ b/server/mutex.c
@@ -58,6 +58,7 @@
     mutex_satisfied,           /* satisfied */
     mutex_signal,              /* signal */
     no_get_fd,                 /* get_fd */
+    no_lookup_name,            /* lookup_name */
     no_close_handle,           /* close_handle */
     mutex_destroy              /* destroy */
 };