BUG: Fixed SubjectHierarchy for nodes with SaveWithScene disabled

For nodes SaveWithScene=False, SH still contained a node ID reference in the scene. This caused incorrectly associating the SH node with an unrelated node existing in the scene with (accidentally) the same node ID.

When scene was loaded that contained invalid DataNode ID (because the node itself was missing from the scene) then the log message tried to print the DataNode pointer that was NULL, causing hang of the scene load (interestingly, the scene loading did not crash, probably some exception handler prevented that).

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25834 3bd1e089-480b-0410-8dfb-8563597acbee