Arbiter not passed to postSolve callback

[robwalch]

This bug was introduced in some recent optimizations. JSHint warns 'arg' is being used out of scope. It used to be defined in the for loop that calls postSolve handlers. That was removed without replacing both instances it is used in. It is still defined farther up in another loop - different context - hence oos instead of not defined. :recycle:

[nornagon]

Good catch, thanks!