Ignored return value for transferFrom call
When burning swap tokens the return value of the `transferFrom` call is ignored. Depending on the token's implementation this could allow an attacker to mint an arbitrary amount of Amp tokens.\\nNote that the severity of this issue could have been Critical if Flexa token was any arbitrarily tokens. We quickly verified that Flexa token implementation would revert if the amount exceeds the allowance, however it might not be the case for other token implementations.\\n```\\nswapToken.transferFrom(\\_from, swapTokenGraveyard, amount);\\n```\\n
The code should be changed like this:\\n```\\nrequire(swapToken.transferFrom(_from, swapTokenGraveyard, amount));\\n```\\n
```\\nswapToken.transferFrom(\\_from, swapTokenGraveyard, amount);\\n```\\n