Duplicating a rubric criterion with 2 levels adds an extra level

Rubric criterion duplication does not result in an exact copy if there are only 2 levels entered. The result is a copy with an additional level worth 1 more point than the highest level of the initial level with the label 'undefined'.

Steps to replicate: add a rubric criterion with 2 levels (zero and something); click duplicate; observe new level with third level added and undefined as label. See attached screenshot (which is on our 3.4.1 but I verified this on moodle.demo.net)