Added a static_cast to avoid build issues under Windows
Added a static_cast to avoid build issues under Windows


ghub/osg,XiaoCC/osg,XiaoCC/osg,omega-hub/osg,koshman86/osg,stmh/osg,koshman86/osg,omega-hub/osg,XiaoCC/osg,stmh/osg,omega-hub/osg,ghub/osg,stmh/osg,stmh/osg,artoolkit/osg,XiaoCC/osg,ntoand/osg,koshman86/osg,ntoand/osg,ntoand/osg,artoolkit/osg,XiaoCC/osg,artoolkit/osg,koshman86/osg,stmh/osg,artoolkit/osg,ghub/osg,ghub/osg,ntoand/osg,omega-hub/osg