Ensure false is preserved in attr serialization

[nickrivadeneira]

Summary

Roundtrip YAML serialization would result in false values coming back as nil. For example:

record = SomeModel.new(some_boolean: false)
dumped = YAML.load(YAML.dump(record))
dumped.some_boolean # => nil

Note about the implementation:

• type and original_attribute have the same presence check. I didn't update these because I wanted to keep the change specific to the problem I encountered, but I'd be happy to update those lines as well.

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[matthewd]

Thanks!

type and original_attribute have the same presence check

Without checking closely, I doubt either of those expect to contain false, so this seems sufficient.