post_update error on running drush updb

on running drush updb I got this error:

>  [warning] Post update function node_title_validation_post_update_8001 not found in file .php
>  [error]  Update failed: node_title_validation_post_update_8001 
 [error]  Update aborted by: node_title_validation_post_update_8001 [7.95 sec, 18.1 MB] 
 [error]  Finished performing updates. [7.95 sec, 18.09 MB] 

The attached patch solved the problem.