Igx Radio Group has no selection when value is 0

## Description  
Describe the issue.

 * igniteui-angular version: above 8
 * browser: any

## Steps to reproduce  

1. Create a radio group, set any radio button to have value 0 
2. Set the value of the form control to be 0

## Result  
Nothing is selected in the radio group.

## Expected result  
The radio button with value 0 should be selected.



