Summary

arbiter fee can be set to 0.

Vulnerability Details

if a buyer decides to set arbiterfee to 0(for whatever reason) but an initial dispute occurs, the arbiter doesn't get anything or the arbiter refuse to resolve dispute and lock the funds.

Recommendations

add check for arbiterFee > 0 in the constructor.
By doing this you can remove the if (i_arbiterFee > 0) statement in the resolveDispute function.