Remove apparently useless next clause in #embedded_params causing method to return nil

This fixes an issue where if a Her model, with a `has_many` association was *built* with an empty array for said association, that an error would be raised when `#to_params` was called on that object.

The root of this problem was a `next` clause in the middle of an `#inject` (which causes the memo, formerly a hash, to become `nil`).

Regardless, it didn't seem to me that the `next` clause was accomplishing anything.  An association skipped here because it was blank would still be included in the `#to_params` result because it was being merged with the existing params.  Removing the offending clause did not break any current specs.