Issue when option value is "null": causes null option to load on init and also error when you try to remove it

[kevduggan]

http://plnkr.co/edit/QuPPgg

I have an option where the value is 'null' (silly I know but that is the data I have been supplied). At some point (I think in selective.js) this gets converted to the null object and it causes issues where by the option is displayed on load and also cannot be deleted.