Resolve: Deletion on mapping containing a struct-with-mapping #602

[nkrishang]

Resolves #602

Although the alert points out struct deletion correctly, the updated test_unpublish_state in ContractPublisher.t.sol shows that the struct deletion is handled correctly.

Particularly: n number of publishContract calls --> one unpublishContract call --> publishContract call again -- does not revive the previously unpublished versions of the contract.