https://github.com/code-423n4/2023-10-badger/blob/main/packages/contracts/contracts/CdpManagerStorage.sol#L269-L274
https://github.com/code-423n4/2023-10-badger/blob/main/packages/contracts/contracts/CdpManagerStorage.sol#L471
When we remove cpd, we zero all its values, but arrayIndex remains.
