COMP: qMRMLSegmentEditorWidget: Fix sign-compare warning

/path/to/Slicer/Modules/Loadable/Segmentations/Widgets/qMRMLSegmentEditorWidget.cxx: In member function ‘void qMRMLSegmentEditorWidget::onSelectSegmentShortcut()’:
/path/to/Projects/Slicer/Modules/Loadable/Segmentations/Widgets/qMRMLSegmentEditorWidget.cxx:2505:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int segmentIndex = 0; segmentIndex < segmentIDs.size(); segmentIndex++)
^

From: Jean-Christophe Fillion-Robin <jchris.fillionr@kitware.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25785 3bd1e089-480b-0410-8dfb-8563597acbee