Avoid negative order total when calculating totals

Signed-off-by: Sam Poyigi <6567634+sampoyigi@users.noreply.github.com>

app/admin/traits/ManagesOrderItems.php

@@ -222,7 +222,7 @@ public function calculateTotals()
             ->where('is_summable', true)
             ->sum('value');
 
-        $orderTotal = $subtotal + $total;
+        $orderTotal = max(0, $subtotal + $total);
 
         $totalItems = $this->orderMenusQuery()
             ->where('order_id', $this->getKey())