Ignore label set images in Pixel Value view
Summary:
Pixel values for labels are shown in the Segmentation view. See T29525 for a more detailed reasoning about why we should ignore label set images in the Pixel Value view at least for now.
Fixes T29525.
Test Plan: Manual testing: In a scene with labeled images, check if the pixel value of the topmost image is shown instead of its segmentation.
Maniphest Tasks: T29525
Differential Revision: https://phabricator.mitk.org/D943