NaN value created when generating benchmark report (regression)

Employee Rostering benchmarker results in `java.lang.IllegalArgumentException: Must be finite.` exception when running.

Refer to reproducer. The variable `unitHeight` is set to NaN in `selectVerticalAutoTickUnit()` method in `NumberAxis.class`, resulting in the exception.

Seems to be a regression as a result of: https://github.com/kiegroup/optaplanner/commit/e3f6762fdad38f9c8e291eaa91beb6816607e46e