Firefox: ui-grid.moveColumns used with grid in disabled fieldset, header follows cursor after click

http://plnkr.co/edit/sfYX2S?p=preview

Create a ui-grid inside of a fieldset with ng-disabled="true". Click (and mouse-up) on one of the column headers. 

In Firefox 46.0.0 and Firefox 46.0.1 the header follows the cursor even after mouse-up as if you are moving the column.
