rzslider sometimes shows NaN for rz-slider-model and sometimes shows value when initialized from javascript

[prabalZwayam]

Steps to reproduce

Demo: http://jsfiddle.net/cwhgLcjv/ (fork this example and update the link)

Expected behaviour

The rz-slider-model should get initialized with value.

Actual behaviour

The rz-slider-model should get initialized with valu but sometimes it show NaN and again get initialzed with value. It periodically changes between actual value and NaN.