Fix: Boolean type searching

* 1.10.0 had issues when searching for boolean data as the search
  extension methods were checking for empty data, but if found they were
  using `''` as the term to filter. It should more accurately just use
  the given data.
* Relates, the `_empty()` method was considering `false` to be empty,
  but not `true`. Both are now considered to be empty.