Error using extension

Error using extension


Is there anyone who can possibly help me with this vague error message?
Screenshot :

What I'm trying to do is to pass a record list (not empty) (and some other stuff) to an extension I wrote myself.

Thanks in advance!
well, the error is not really that vague, but we cannot do much with the code itself.

the issue is simply you are assigning stuff to something that is not there...

probably an off-by-1 issue...