Yep, there's a missing function. Add this code at the end of 'application/views/reporting/index.php':
<script>
og.deleteReport = function(id){
if(confirm(lang('delete report confirmation'))){
og.openLink(og.getUrl('reporting', 'delete_custom_report', {id: id}));
}
};
</script>
This will be fixed for next version.
Thanks.