Game crashes while battling in someone else's secret base

[Former user]

The issue is as it follows: I was visiting someone else's secret base (IDK if it has something to do with it). At a point, I find an Aroma Veil Spritzee. I switch in my Mold Breaker Axew and the game crashes with the following error.

Script 'PokeBattle_Battler' line 2832: NoMethodError occurred.

undefined method '>' for nil:NilClass