BHV-13376: make Spotlight can't throws exception in freeze function

## Issue
Spotlight throws exception when using VideoPlayer

## Problem
After 2.5.0, _oCurrent is 'null' when spotlight is not pointing any control. So whenever user/framework call freeze function when _oCurrent is null, freeze function throws exception and script is stopped. It has a risk for triggering abnormal behavior on runtime

## Fix
make Spotlight can't throws exception in freeze function and change to give a warning msg.

Enyo-DCO-1.1-Signed-off-by: Sungbae Cho sb.cho@lge.com