Prevent possibility to select NaN for an hour, minute and second value.

Issue is affecting Chromium (my version is 33.0.1750.152). Only sideBySide: true options is used - http://jsfiddle.net/G3mfH/2/.

Steps to reproduce:

* Click the hour or minute value of the timepicker. List of hours/minutes appears.
* Click exactly between two values when no hover state is shown. 

![side-by-side_invalid_value_selected](https://cloud.githubusercontent.com/assets/4487978/2745514/57b321ea-c737-11e3-86e4-b9a197c2022d.png)