Presale - should not allow zero value contributions
The Presale accepts zero value contributions emitting a contribution event if none of the Aragon components (TokenManager, MinimeToken) raises an exception.\\n```\\nfunction contribute(address \\_contributor, uint256 \\_value) external payable nonReentrant auth(CONTRIBUTE\\_ROLE) {\\n    require(state() == State.Funding, ERROR\\_INVALID\\_STATE);\\n\\n    if (contributionToken == ETH) {\\n        require(msg.value == \\_value, ERROR\\_INVALID\\_CONTRIBUTE\\_VALUE);\\n    } else {\\n        require(msg.value == 0,      ERROR\\_INVALID\\_CONTRIBUTE\\_VALUE);\\n    }\\n\\n    \\_contribute(\\_contributor, \\_value);\\n}\\n```\\n
Reject zero value `ETH` or `ERC20` contributions.
```\\nfunction contribute(address \\_contributor, uint256 \\_value) external payable nonReentrant auth(CONTRIBUTE\\_ROLE) {\\n    require(state() == State.Funding, ERROR\\_INVALID\\_STATE);\\n\\n    if (contributionToken == ETH) {\\n        require(msg.value == \\_value, ERROR\\_INVALID\\_CONTRIBUTE\\_VALUE);\\n    } else {\\n        require(msg.value == 0,      ERROR\\_INVALID\\_CONTRIBUTE\\_VALUE);\\n    }\\n\\n    \\_contribute(\\_contributor, \\_value);\\n}\\n```\\n