NestedReserve: Redundant valid token address checks

[code423n4]

Handle

GreyArt

Vulnerability details

Impact

The transferFromFactory() function is missing the valid(address(_token)) modifier that is present in the transfer() and withdraw() functions.

It is in our opinion that these sanity checks on the token address are redundant, because the transaction will revert anyway in the SafeERC20 library.

Recommended Mitigation Steps

Either add in the modifier check for the transferFromFactory() function. Alternatively, remove them from all the functions as a gas optimization.

[maximebrugel]

Remove valid modifier but keep zero address check on _recipient in transfer() (we don't want to burn).