Bug: getting ID of species.battleOnly when it's an array

[andrebastosdias]

pokemon-showdown/sim/dex-species.ts

Lines 464 to 467 in 9ec7c4a

	} else if (species.battleOnly) {
	species.tier = this.dex.data.FormatsData[toID(species.battleOnly)].tier || 'Illegal';
	species.doublesTier = this.dex.data.FormatsData[toID(species.battleOnly)].doublesTier || 'Illegal';
	species.natDexTier = this.dex.data.FormatsData[toID(species.battleOnly)].natDexTier || 'Illegal';

I created a mod where I set isNonstandard = "Past" for all Zygarde forms. However, I didn't manually set tier, doublesTier, and natDexTier to Illegal. When Zygarde-Complete attempts to derive the tiers from its base forms, it converts the array ["Zygarde", "Zygarde-10%"] into an ID. Consequently, it ends up trying to fetch the tier of an undefined element, causing a crash.

I'm unsure if this is the only part of the code affected, but it seems somewhat inefficient to have to set the tiers of all non-standard to Illegal just to avoid this bug (although this currently only impacts Zygarde-Complete and Necrozma-Ultra). Setting the tiers to Illegal avoids entering this part of the code.