In some cases, the remove item X button is not hidden when there is no
selection made from the dropdown. This is not as usable, since there's
no item to clear, hence an effective noop.
The condition I saw seeing this issue arise is in single selects with
a placeholder value, a selection has been made, and then cleared: the
button HTML remains.
To fix, add some styles to hide the button if the select doesn't have a
value selected, in this case keying off of it's parents `data-value`
property.
fixes#684