BUG: Update EMSegment to fix -Winfinite-recursion warning

This commit fixes the following warning:

/path/to/Slicer-build/EMSegment/MRML/vtkMRMLEMSVolumeCollectionNode.h:64:3: warning: all paths through this function will call itself [-Winfinite-recursion]
{
^

Updates:

• r17126 | jcfr | 2017-03-12 14:33:29 -0400 (Sun, 12 Mar 2017) | 1 line
  COMP: vtkMRMLEMSVolumeCollectionNode: Fix -Winfinite-recursion warning

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25818 3bd1e089-480b-0410-8dfb-8563597acbee