Option element inside optgroup is not correctly marked as selected

If select tag contains multiple optgroup elements then options inside optgroups other than the first one are not correctly marked as selected. 

**See:**  http://codepen.io/anon/pen/jWqWBd
**Reproducable:** always
**Browsers:** Chrome ver. 47.0.2526.80 m
**Operating system:** Windows 7

Occurs on version 1.4.8. The issue is not replicable on version 1.4.7 and the previous ones. 
