How to add unique visitors in the 'All Website Dashboard'?

I want to add unique visitors in the ‘All Website Dashboard’ page, but fail to fetch nb_uniq_visitors data.

show’s the code(before change):


~/piwik/plugins/MultiSites/angularjs/dashboard/dashboard-model.service.js
function fetchAllSites() {
            ......
            var params = {
                module: 'MultiSites',
                action: 'getAllWithGroups',
                hideMetricsDoc: '1',
                filter_sort_order: 'asc',
                filter_limit: model.pageSize,
                filter_offset: getCurrentPagingOffsetStart(),
                showColumns: 'label,nb_visits,nb_pageviews,visits_evolution,pageviews_evolution,revenue_evolution,nb_actions,revenue'
            };
            .....
        }

show’s the code(modified)


~/piwik/plugins/MultiSites/angularjs/dashboard/dashboard-model.service.js
function fetchAllSites() {
            ......
            var params = {
                module: 'MultiSites',
                action: 'getAllWithGroups',
                hideMetricsDoc: '1',
                filter_sort_order: 'asc',
                filter_limit: model.pageSize,
                filter_offset: getCurrentPagingOffsetStart(),
                showColumns: 'nb_uniq_visitors,label,nb_visits,nb_pageviews,visits_evolution,pageviews_evolution,revenue_evolution,nb_actions,revenue'
            };
            .....
        }

Or I do something wrong? Any idea about this?