Submitted by shw
A possible divide-by-zero error could happen in the getSherXPerBlock(uint256, IERC20) function of PoolBase when the totalSupply of lockToken and _lock are both 0.
Recommend checking  if baseData().lockToken.totalSupply().add(_lock) equals to 0 before line 214. If so, then return 0.
Evert0x (Sherlock) confirmed
