[Question] Essentials Error Help

When I hit New Game or Continue in my game I get this

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Pokemon Sienna Beta 1.3
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Exception: NoMethodError

Message: undefined method `*' for nil:NilClass

Game_Character_1:198:in `screen_z'

Sprite_Character:148:in `update_or'

PerspectiveTilemap:430:in `shadow_update'

Shadow:179:in `update'

Sprite_Character:37:in `perspectivetilemap_initialize'

PerspectiveTilemap:424:in `shadow_initialize'

Shadow:152:in `initialize'

Spriteset_Map:162:in `new'

Spriteset_Map:162:in `_animationSprite_initialize'

Spriteset_Map:161:in `each'



This exception was logged in ./errorlog.txt.

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OK
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I just replaced the ow sprite and I got it to work but the next time I got this