Help! Error message in Essentials 17.2

Someone help! I keep getting an error message whenever I run into a wild Pokemon in Pokemon Essentials. It says this:

[Pokémon Essentials version 17.2]
Exception: NoMethodError
Message: undefined method `length' for nil:NilClass
PItem_Bag:101:in `pbQuantity'
PItem_Bag:106:in `pbHasItem?'
PField_Encounters:345:in `pbGenerateWildPokemon'
PField_Battles:88:in `pbWildBattle'
PField_Field:387:in `pbBattleOnStepTaken'
PField_Field:368:in `pbOnStepTaken'
Game_Player:461:in `update_old'
Game_Player_Visuals:71:in `update'
Scene_Map:164:in `update'
Scene_Map:161:in `loop'
[Pokémon Essentials version 17.2]
Exception: NoMethodError
Message: undefined method `length' for nil:NilClass
PItem_Bag:101:in `pbQuantity'
PItem_Bag:106:in `pbHasItem?'
PField_Encounters:345:in `pbGenerateWildPokemon'
PField_Battles:88:in `pbWildBattle'
PField_Field:387:in `pbBattleOnStepTaken'
PField_Field:368:in `pbOnStepTaken'
Game_Player:461:in `update_old'
Game_Player_Visuals:71:in `update'
Scene_Map:164:in `update'
Scene_Map:161:in `loop'

and then the game crashes. If someone knows what's going on, can you please help me? Trainer battles work fine, it's just wild Pokemon battles, so I don't know what I did wrong.

whoops posted the error twice
oh well

I have the same question. Its strange because random wild encounters work fine, its only scripted event battles, even the examples like Mew and Deoxys have the same error message as above.

Hold CTRL while running the game in debug

Or try to delete your save file and start a new game.