Fix stale aggregate/group_value sort when group by is disabled

When sortBy was set to 'aggregate' or 'group_value' from a previous
group by session, disabling group by would pass the stale sort column
to the base query causing a column not found error.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: SimonBarrettACT

src/ReportBuilder.php

@@ -25,6 +25,11 @@ public function rowsQuery()
         $query = parent::rowsQuery();
 
         if (! $this->hasGroupBy()) {
+            if (in_array($this->sortBy, ['aggregate', 'group_value'], true)) {
+                $this->sortBy = '';
+                $query->reorder();
+            }
+
             return $query;
         }