If a user accidentally sent ether to the Vault contract, the ether will be stuck in the vault with no way to retrieve them.
https://github.com/code-423n4/2022-07-fractional/blob/8f2697ae727c60c93ea47276f8fa128369abfe51/src/Vault.sol#L32
Consider if there is a need for the Vault contract to receive ethers. Otherwise, remove it.
