Hi,
I cannot seem to replicate this. However, if I understand correctly, you were using an old save?
If that is indeed the case, I would say that is the reason. You see, in the old system the variables could only have one value i.e.
variable = "fox" which mean the preallocation would have been done as variable = "" vs. now it can have multiple values
variable = ["fox", "wolf"] and preallocation is done as variable = [].
I think this is the cause of the error. It should work fine with a new save, in an old save there is a disconnect between the preallocations of the variable.
Sorry for the inconvenience! Updates tend to break old saves (assuming you were indeed using an old save).
Edit: And thank you!