Bug - anchor to null on hover over the responses buttons (before beginning an exercise)

Summary:
Steps to follow to replicate the bug:
1. open Minuet
2. open an exercise
3. before pressing "New Question", hover over the responses ("your choises") buttons
4. in the console, two "null" error will appear

[[ https://youtu.be/7hpGvvpUklU | link on Youtube ]]

Reviewers: sandroandrade

Subscribers: stefant

Tags: #minuet

Differential Revision: https://phabricator.kde.org/D4326