Core Data and Transient Properties

For a while, I've been having this problem show up in the debugger: 

[ valueForUndefinedKey:]: the entity EVECDCharacter is not key value coding-compliant for the key (null).

I suspected I knew where it was but could not, for the life of me, figure out why it was crashing. My mistake was that I wasn't paying attention to the fact that the line I (correctly) thought was causing the crash was done in a separate thread. So when I did realize this and took a look at the stack trace, the above picture is what I got.

I don't know what I should be more concerned with: The huge stack size or the fact that a transient value was being requested. Line #5 is specifically where the call gets made. In that call, a request for the skill is requested. However, the skill doesn't get set until later in the skill queue API parsing.

For now the easy solution would be just to do a simple check to make sure the value exists. It is something I'd like to find an explanation for, though.