Noticed this when using the graph visual. It seems to only happen when selecting the right check box first. Randomly it happens with the left checkbox. The label sets to Undefined:Undefined.
To duplicate make sure to check the Right checkbox first. Then checking the Left checkbox will give you an undefined:Undefined both times.
If you check the left checkbox first then the right checkbox it will have the right label. So sort of a work around until the bug is fixed, or identified to just be my install. Not sure what saved graphs look like yet, Iāl test that next.