EDIT: i just noticed you have v0.27.3, which is newer than the release here on f95. so below advice might not work.
Somehow your save has got one of the "crowd" objects (schoolboys or schoolgirls) into the "contact_list" variable.
There's a save compatibility reference to that var, so maybe it was broken at some point and was supposed to be fixed.
Anyway, if you open console (enable dev mode first if needed) and run the following, then save game, it might fix it:
Code:
contact_list = [mom, slacker, jock, nerd, cheerleader, firebrand, principal, student, busty, goth]