Villager experience bar displays incorrectly

A villager's experience bar seems to display incorrectly if the amount of experience is over the amount the bar can display. Error is on the right of the screenshot.
How to reproduce:
1. Create a novice farmer villager by summoning a villager next to a composter.
2. Open the farmer's GUI.
3. Trade all the carrots and potatoes you can with the farmer without closing the GUI.