Handle uninitialized segmentations in interpolator

Summary:
Invoke an itk::AbortEvent() when the observed segmentation gets invalid.
Also, remove observers that were added before.

Disable interpolation in GUI if interpolator aborted.

Fixes T28385.

Test Plan: See reproduction steps in T28385.

Reviewers: O1 MITK Reviewer Group I, kalali

Reviewed By: O1 MITK Reviewer Group I, kalali

Subscribers: kalali

Maniphest Tasks: T28385

Differential Revision: https://phabricator.mitk.org/D519