COMP: Update EMSegment: Fix "comparison of pointer with integer zero" warning

//----------
/home/jcfr/Projects/Slicer-Debug/EMSegment/AMF/vtkImageLevelSets.cxx: In member function ‘unsigned char vtkImageLevelSets::CheckConvergence()’:
/home/jcfr/Projects/Slicer-Debug/EMSegment/AMF/vtkImageLevelSets.cxx:1301:24: warning: ordered comparison of pointer with integer zero [-Wextra]
if (this->u[p] <= 0) total++;
^
/home/jcfr/Projects/Slicer-Debug/EMSegment/AMF/vtkImageLevelSets.cxx:1306:65: warning: ordered comparison of pointer with integer zero [-Wextra]
if ((this->stored_seg[p] == ON_STORED) && (this->u[p] > 0))
^
/home/jcfr/Projects/Slicer-Debug/EMSegment/AMF/vtkImageLevelSets.cxx:1309:66: warning: ordered comparison of pointer with integer zero [-Wextra]
if ((this->stored_seg[p] == OFF_STORED) && (this->u[p] <= 0))
^
/home/jcfr/Projects/Slicer-Debug/EMSegment/AMF/vtkImageLevelSets.cxx:1313:24: warning: ordered comparison of pointer with integer zero [-Wextra]
if (this->u[p] <= 0) ^
//----------

Co-authored-by: Kilian Pohl <pohl.kilian@gmail.com>
Reviewed-by: Steve Pieper <pieper@bwh.harvard.edu>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@24685 3bd1e089-480b-0410-8dfb-8563597acbee