Fix missing checks for ivs and evs for the encounters

[Palbolsky]

Description

The issue has been reported here: https://discord.com/channels/143824995867557888/1462474485348175973

The check for the ivs and evs in the usePokemonBattler hook was not working due to an implementation error. This PR fixes the check.

Tests to perform

• When they're adding a creature in a group, trainer or quest earning, the user cannot add the creature if the ivs or evs is empty or not between 0 and 9999.
• When they're editing a creature in a group, trainer or quest earning, the user cannot close the editor if the creature has the iv or ev is not between 0 and 9999. Empty value is allowed.