Change group by clause from "day" to "created"

src/views/default/panels/trail/chart.php

@@ -17,7 +17,7 @@
     ->where(['between', 'created',
         date('Y-m-d 00:00:00', $startDate),
         date('Y-m-d 23:59:59')])
-    ->groupBy("day")->indexBy('day')->column();
+    ->groupBy("created")->indexBy('day')->column();
 
 // format dates properly
 $formattedData = [];