[Scripting Question] "Set Tailwind When Sent Out" ability code crashes game with nonsense error message. Who can help me fix this?

[SuperSpyroDragon64]

Battle::AbilityEffects::OnSwitchIn.add(:STORMWIND,
  proc { |ability, battler, battle, switch_in|
battler.pbOwnSide.effects[PBEffects::Tailwind] = 5
    @battle.pbDisplay(_INTL("Tailwind intensified!"))
  }
)

Everything seems fine to me, but is it fine? It's crashing the game any time anyone with this ability gets sent out. It's supposed to set Tailwind when your Pokemon is sent out, and be to Tailwind what Drought is for Sunny Day: An automatic use of that move in ability form.

If it helps, here's the error message:

[Pokémon Essentials version 20.1]
[v20.1 Hotfixes 1.0.4]

Exception: NoMethodError
Message: undefined method `[]=' for true:TrueClass

Backtrace:
[Essentials Deluxe] Pokedex.rb:332:in `register'
[ZUD Mechanics] Battle_Overrides.rb:58:in `pbSetSeen'
151:Battle_ActionSwitching:293:in `block in pbSendOut'
151:Battle_ActionSwitching:291:in `each'
151:Battle_ActionSwitching:291:in `pbSendOut'
148:Battle_StartAndEnd:240:in `block in pbStartBattleSendOut'
148:Battle_StartAndEnd:197:in `each'
148:Battle_StartAndEnd:197:in `pbStartBattleSendOut'
148:Battle_StartAndEnd:284:in `pbStartBattleCore'
148:Battle_StartAndEnd:270:in `pbStartBattle'

 

[SuperSpyroDragon64]

Update: Adding another = didn't fix it.

Battle::AbilityEffects::OnSwitchIn.add(:STORMWIND,
  proc { |ability, battler, battle, switch_in|
battler.pbOwnSide.effects[PBEffects::Tailwind] == 5
    @battle.pbDisplay(_INTL("Tailwind intensified!"))
  }
)

 

[Lucidious89]

This error has absolutely nothing to do with your ability. The error is occurring because you didn't follow the instructions when installing Essentials Deluxe, and didn't start a new game like you were supposed to.

Also, you only want a single equation sign for your ability. The way you originally had it was correct. Also, remove the @ in front of @battle.