Fix error propagation in iterator
Fix error propagation in iterator

This fixes a minor issue where the iterator, after calling the `run` function, doesn't pass along its error to the callback.
ethereumjs/ethereumjs-vm,ethereum/ethereumjs-vm,ethereumjs/ethereumjs-vm,ethereumjs/ethereumjs-vm,ethereumjs/ethereumjs-vm,ethereumjs/ethereumjs-vm