Submitted by DadeKuma, also found by chaduke
https://github.com/code-423n4/2023-01-popcorn/blob/main/src/vault/adapter/abstracts/AdapterBase.sol#L392 
https://github.com/code-423n4/2023-01-popcorn/blob/main/src/vault/adapter/abstracts/AdapterBase.sol#L110-L122 
https://github.com/code-423n4/2023-01-popcorn/blob/main/src/vault/adapter/abstracts/AdapterBase.sol#L147-L165
Users could receive 0 shares and thus lose their entire investment when making a deposit.
Alice calls deposit with 999 assets, with herself as the receiver
Shares are calculated through _previewDeposit, which uses _convertToShares rounding down
With specific conditions, the share calculation will round to zero.
Lets suppose that _totalSupply = 100_000 and  _totalAssets = 100_000_000, then:
which rounds to zero, so total shares are 0.
Finally, the deposit is completed, and the adapter mints 0 shares.
Alice has lost 999 assets and she has received nothing in return.
Revert the transaction when a deposit would result in 0 shares minted.
RedVeil (Popcorn) confirmed, but disagreed with severity 
LSDan (judge) decreased severity to Medium 
