BHV-12792 : add checking routine for value on refresh function

## Issue
TimePicker: Picker Disappears when Defaulted Locale is Reselected

## Cause
After Edwin added fix( 0338c37f ), there was no checking statement about value's status
Currently, locale can be changed when 'value' is null, 'this.value.getTime' makes error msg at that time.

## Fix
Add checking routine for value on refresh function