Before people were unable to remove coordinator fees from an order cycle because Rails was converting the empty :coordinator_fee_ids array paramter into nil. This issue was introduced to Rails in v4.0.0.beta1 and isn't fixed until v5.0.0.beta1
Another way to fix this could be to do something like 'params[:coordinator_fee_ids] ||= []' but it seems like this issue could problems in other parts of the app so a more general fix might be better.
Fixes#6224