wmde/ValueView — pull request #40 by adrianlang (2014-03-28 11:26:06+00:00)
Title: Don't throw an error when setting null value on a ValueView

Since DataValues have to have a `toJSON` method and `_value` and `value` are guaranteed to be null or a DataValue, the check for `toJSON` is not needed. However, we definitely have to check whether `value` actually is null.