`Relation.where` does not function on missing values as expected

[srfc]

Bug Report

Relation.where does not function on missing values as expected.

Expected Behavior

• given a selection function that always, regardless of input, produces true, where should return all Records in the Relation

Actual Behavior

• the result set is missing any Records that are missing values in the specified column

Steps to Reproduce the Problem

1. create Relation with missing values for some Records on in one column
2. execute MissingValuesRelation.where(MissingValuesRelation.someColumn, (_: Any) => true)
3. result set is missing all Records that are missing values in someColumn