confirm if lengths are equal before looping

[code423n4]

Handle

hack3r-0m

Vulnerability details

https://github.com/XDeFi-tech/xdefi-distribution/blob/master/contracts/XDEFIDistribution.sol#L80

check the length of durations_ and multipliers is equal and revert if it is not resulting in gas savings rather than delayed revert.

[deluca-mike]

We try to reduce gas costs for happy path, not for sad path. Assuming lengths are equal (which they will be in the overwhelming majority of the time), it is cheaper not to check them. Further, most wallets (and certainly the one we use) will alert the user if a transaction is going to fail, so it will never waste gas anyway.

[deluca-mike]

Duplicate #38