Fix issue with volume label maps and only one label
This change ensures that a valid scale is computed for a single label label map mask volume.
Added a test - TestGPURayCastLabelMap1Label for the regression
Fixes #17719 (closed)
This change ensures that a valid scale is computed for a single label label map mask volume.
Added a test - TestGPURayCastLabelMap1Label for the regression
Fixes #17719 (closed)