WhitelistVerifier.sol

Verifies pre-approved tokens being imported via the TokenImporter.

[LOW] Cannot Un-Whitelist a Memecoin

It is impossible to un-whitelist a memecoin / sender combination as _status is not used, and it's required that both the _memecoin and _sender address are not zero addresses.

There are two solutions that we forsee for this issue:

1. This means an arbitrary address (e.g. 0xdEaD) would need to be used. We would recommend removing the zero address check for the sender and then just allowing a zero address sender to be set. This would be a simpler solution and would allow for the _status parameter to be deprecated.
2. Alternatively, you could introduce a 3d array to map memecoin -> sender -> status. This would give more flexibility to the whitelisting approach and allow multiple senders to handle a memecoin import.