COMP: qSlicerApplication: Fix unused variable warning in release build

This commit fixes the following warning:

/path/to/Slicer/Base/QTGUI/qSlicerApplication.cxx: In member function ‘virtual void qSlicerApplication::handlePreApplicationCommandLineArguments()’:
/path/to/Slicer/Base/QTGUI/qSlicerApplication.cxx:451:30: warning: unused variable ‘options’ [-Wunused-variable]
qSlicerCoreCommandOptions* options = this->coreCommandOptions();
^

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

git-svn-id: http://svn.slicer.org/Slicer4/trunk@24896 3bd1e089-480b-0410-8dfb-8563597acbee