That error means you are trying to delete something that doesnt exist, first of all check if you referenced it correctly (Wrong location or maybe a typo are the most common)
If the code is "correct", then check if that node is not being deleted before by something else.
Still, it seems like we're missing a lot of code to reach the cause... For example, where does this "area" var come from in the die(area)
function?
By the way, to avoid problems, the player's root node should be a KinematicBody
or RigidBody
not an AnimatedSprite