#### Added
* `is empty` and `is not empty` operators for fields with predefined choices.
* Option to specify a custom value for the `contains` operator when fields have predefined choices.
#### Fixed
* Incorrect results returned when a `Current User Role` filter option was combined with another condition using an `OR` statement.
* PHP warning when filter condition value is left empty.
* Field conditional logic on a field from a joined form (via Multiple Forms extension) did not work.
