[ic] expire error and SessionExpire

[Sim Zacks]

I get the following error when I run expire or expireall. Does anyone know what causes this?
"Can't call method "set_row" on an undefined value at (eval 1) line 7, <IN> chunk 2."

Also I did not have a SessionExpire or a SaveExpire option in my catalog.cfg so I added it after reading a post 
that asked a question about it.
Iadded to the top of my catalog.cfg ffile
SessionExpire 1 hour
SaveExpire 1 day
I expect this means that if you have something in your shopping cart and leave your machine alone for over an hour then what is in your shopping cart gets removed. 
Please let me know if this is not the case.

I am using version 4.5.5 and I can not switch to the newest version every time a change is made unless there is a problem that is really affecting me, so if this is a version problem pl;ease let me know.

Sim