[kcms/launch] Avoid infinite loop in button handling

Summary:
When visiting Applications / Launch Feedback the star, indicating a edit
on this page, begin to flicker.

QQC2 allows us to fix it properly.

BUG: 403950

Test Plan: Made some changes

Reviewers: #plasma, broulik

Reviewed By: #plasma, broulik

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D18748