Fix issue with generating enemy modifiers

src/battle-phases.ts

@@ -635,7 +635,7 @@ export class SummonPhase extends PartyMemberPokemonPhase {
             this.scene.field.add(pokemon);
             if (!this.player) {
               const playerPokemon = this.scene.getPlayerPokemon() as Pokemon;
-              if (playerPokemon.visible)
+              if (playerPokemon?.visible)
                 this.scene.field.moveBelow(pokemon, playerPokemon);
               this.scene.currentBattle.seenEnemyPartyMemberIds.add(pokemon.id);
               this.scene.updateModifiers(false);