KCM/Component email: simplify code
Summary:
Clean up adding entries for Added Associations section of mimeapplist
Just find the application set if it is not found by the normal query.
Also add a constant and reuse one.
Reviewers: Plasma, ervin, bport, crossi
Reviewed By: ervin, bport
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D27116