fix segfault : check sample not empty
fix segfault : check sample not empty

aureooms-ulb-2010-2015/2013-2014-infoh413-projects,aureooms-ulb-2010-2015/2013-2014-infoh413-projects,aureooms-ulb-2010-2015/2013-2014-infoh413-projects,aureooms-ulb-2010-2015/2013-2014-infoh413-projects