FinderTrait addWheres() assumes 'IS' and 'IS NOT' operators will be followed by null

[agerbens]

Description

In the FinderTrait's addWheres() function, if the operator is either IS or IS NOT it automatically creates IsNull or IsNotNull predicates, assuming that the user wants to check for null.

IS and IS NOT can also be used to check boolean values.
https://dev.mysql.com/doc/refman/5.1/en/comparison-operators.html#operator_is

Details

https://github.com/synapsestudios/synapse-base/blob/master/src/Synapse/Mapper/FinderTrait.php#L298