refs #1816 make sure we get a date string and not an array of date strings in...

refs #1816 make sure we get a date string and not an array of date strings in case for instance when handling period=month

core/API/DataTableManipulator/ReportTotalsCalculator.php

@@ -163,7 +163,7 @@ class ReportTotalsCalculator extends DataTableManipulator
                 $request['date']   = $period->getRangeString();
                 $request['period'] = 'range';
             } else {
-                $request['date']   = $period->toString();
+                $request['date']   = $period->getDateStart()->toString();
                 $request['period'] = $period->getLabel();
             }
         }