ComboBox input error on required field

Enonic version: 6.7.0-RC1
OS: Windows 7 / Chrome 51.0.2704.103 m

I have a mixin with a ComboBox with occurences set to minimum=“1” and maximum=“1”. There is also a default value set on the ComboBox. This mixin is used inside an item-set, named Translation, with occurences set to minimum=“0” and maximum=“0”. Whenever I click on “Add Translation” the ComboBox shows up with the default value set. If I then click to remove the default value and attempt to click on a different value in the ComboBox, a javascript error occurs; “Cannot read property ‘isValid’ of undefined”.

Here’s a screenshot:


This is a known bug that will be fixed before the release of 6.7.