Check explicitly for undefined range value in Slider#updateValueFromEvent.
Check explicitly for undefined range value in Slider#updateValueFromEvent.

Truthiness test causes a bug when a range value is 0 (or potentially some other falsy value).

ihmeuw/ihme-ui,ihmeuw/ihme-ui,ihmeuw/beaut,ihmeuw/ihme-ui,ihmeuw/beaut,ihmeuw/beaut