Commit ae828cd3b092 ("LU-4684 llite: add lock for dir layout data") for

https://review.whamcloud.com/#/c/32946/

changed how op_data was allocated, with consequence that failure is reported as NULL rarther than ERR_PTR(-ENOMEM).  The error handling code was not updated to match.

So a memory allocation failure will cause a NULL pointer dereference.