Allow choice value to be 0

I have a choice which value is 0, and it seems like nothing happens when I click this option. ( It does not trigger the change event )

const choices = [{
  value: 0,
  label: 'Label 1'
}]

I tried to change the value to any number other than zero, and it works fine.

[jeffperrin]

Looks like this is caused by this line: https://github.com/jshjohnson/Choices/blob/master/assets/scripts/src/choices.js#L1142

Anything ‘falsey’ will not trigger the change event (ie; 0 or an empty string). I’m not sure what the original reason for this check was, but it seems like it should explicitly be looking for null or undefined instead.

[jonnyscholes]

Great to see this is fixed! Would it be possible to cherry pick this into master as a patch release? More than happy to submit a PR to master with just the changes from #349 if thats helpful 😃