Move non-optional ModelSpy dependency to ctor
Summary:
A ModelSpy cannot work without a model, and there is no point
re-setting it, so it should be set in the ctor only.
Reviewers: KDE PIM, dvratil
Reviewed By: KDE PIM, dvratil
Subscribers: dvratil, kde-pim
Tags: KDE PIM
Differential Revision: https://phabricator.kde.org/D16557