Introduce nullptr checks in PlanarFigureInteractor to avoid nullptr exception
Summary:
Clean class
Add nullptr checks to prevent crashes
Test Plan: manual
Reviewers: kislinsk, O1 MITK Reviewer Group I
Reviewed By: kislinsk, O1 MITK Reviewer Group I
Subscribers: kalali, floca, kislinsk
Maniphest Tasks: T27061
Differential Revision: https://phabricator.mitk.org/D384