Revert when not enough precision to assign a delegation share

[abarmat]

Description

A delegation pool holds tokens deposited by delegators as well as rewards. When rewards start accruing, depositing a very very small amount of new tokens by a delegator could lead to zero shares being assigned.

uint256 shares = (pool.tokens == 0)
            ? delegatedTokens
            : delegatedTokens.mul(pool.shares).div(pool.tokens)

Solution

Revert in any condition when no shares are assigned.

[davekaj]

rebase the conflicts but otherwise good