I tried it with 19c, and the mod doesn't cause the error to appear.
However, I'm not sure the in game effects are happening as intended. Sometimes the game matched girls portraits to their auto gen description, but more often than not it's seemingly random assignment of pictures. (The girl is a futa human teen large tits, but the picture assigned is an elf female adult small tits).
I used the sorting / naming tool pack editor to apply genders, races, and so on to each picture I have in the portraits folder.
examples:
\AppData\Roaming\Strive\portraits\Orc\Female\Teen\Purple GreenSkin TitsM AssM [4938b45e].jpg
\AppData\Roaming\Strive\portraits\HalfkinCat\Female\Teen\Black SkinL TitsM AssB preg [c831d780].jpg
\AppData\Roaming\Strive\bodies\Human\Female\Adult\Green SkinL TitsB AssB 2 [3950a0d6].jpg
and so on.
Does that look correct?