Fix sidebar view regression of not prompting about unsaved changes
Summary:
When you switch module with unsaved changes the other modes prompt if
you want to save the changes. Sidebar mode did not.
BUG: 392160
Test Plan:
Made a change, clicked another module. Got a prompt.
Clicked apply, it applied then changed
Tried again
Clicked cancel, it didn't change
Reviewers: Plasma, broulik
Reviewed By: Plasma, broulik
Subscribers: broulik, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D12686