Hmm, I think I know what that is from, I had looked it up when someone posted the same error in another thread. Theirs was at 1131, but I imagine that just means you have an extra line of code somewhere before that in your version of globals.gd. The error in question is most likely a result of the impregnation function not being passed a "father" person, like would happen during most of the sex jobs, or randomly to someone being a housepet or sleeping in the kennel. The random events that involve sex with a random "male" character that isn't you or a slave will also pass no father to that function.
Original impregnation would create a random generic person to be the father in those cases but the edits to how breeding slaves works broke that functionality. I have made a bunch of changes to that function and the ones that use the outputs from it myself, but haven't gotten around to testing them yet, if they work when I do test them I will post them.