Bug fix for attempting to build a Document with nil for attributes

# Why?
See https://github.com/RevSpringPhoenix/arkenstone/pull/72

# What changed?
See https://github.com/RevSpringPhoenix/arkenstone/pull/72
NOW WITH TESTS!
Unused block argument - `value`. If it's necessary, use `_` or `_value` as an argument name to indicate that it won't be used.