Issues 3665 and 3671: fix for phantom data in work form

Issues 3665 and 3671: fix for phantom data in work form due to Rails association bug. Works are now told explicitly not to pull in chapters with null foreign keys.

Rails bug (not getting fixed until Rails 4): https://github.com/rails/rails/issues/5215

https://code.google.com/p/otwarchive/issues/detail?id=3665
https://code.google.com/p/otwarchive/issues/detail?id=3671