Fix printing of email addresses

Summary:
The "emails" property used to be a QStringList, which can't be displayed
as such. It's a list of KContact::Email gadgets after D20540.

Reviewers: mlaurent

Reviewed By: mlaurent

Subscribers: kde-pim

Tags: #kde_pim

Differential Revision: https://phabricator.kde.org/D20541