fix: report aggregate by column (#670)

Author: andreiio

app/Reports/Queries/Child/C31.php

@@ -28,6 +28,11 @@ public static function dateColumn(string $type): string
         return 'community_activities.created_at';
     }
 
+    public static function aggregateByColumn(): string
+    {
+        return 'community_activities.id';
+    }
+
     public static function includeLatestBeforeRange(): bool
     {
         return false;