MultipleWinners - setNumberOfWinners does not enforce count>0
The constructor of `MultipleWinners` enforces that the argument `_numberOfWinners > 0` while `setNumberOfWinners` does not. A careless or malicious admin might set `__numberOfWinners` to zero to cause the `distribute()` method to throw and not pay out any winners.\\nenforced in the constructor\\n```\\nrequire(\\_numberOfWinners > 0, "MultipleWinners/num-gt-zero");\\n```\\n\\nnot enforced when updating the value at a later stage\\n```\\nfunction setNumberOfWinners(uint256 count) external onlyOwner {\\n  \\_\\_numberOfWinners = count;\\n\\n  emit NumberOfWinnersSet(count);\\n}\\n```\\n
Require that `numberOfWinners > 0`.
```\\nrequire(\\_numberOfWinners > 0, "MultipleWinners/num-gt-zero");\\n```\\n