server: Return an error in get_handle_unix_name for objects that don't have a file name.

This way we fall back to retrieving the Win32 name.

server/fd.c

@@ -2254,6 +2254,7 @@ DECL_HANDLER(get_handle_unix_name)
             if (name_len <= get_reply_max_size()) set_reply_data( fd->unix_name, name_len );
             else set_error( STATUS_BUFFER_OVERFLOW );
         }
+        else set_error( STATUS_OBJECT_TYPE_MISMATCH );
         release_object( fd );
     }
 }