fix replace the negative subscription problem

app/Http/Controllers/User/OrderController.php

@@ -89,7 +89,8 @@ class OrderController extends Controller
             $trafficUnitPrice = $trafficUnitPrice - ($trafficUnitPrice * $user->discount / 100);
         }
         $notUsedTrafficPrice = $plan->transfer_enable - (($user->u + $user->d) / 1073741824);
-        return $trafficUnitPrice * $notUsedTrafficPrice;
+        $result = $trafficUnitPrice * $notUsedTrafficPrice;
+        return $result ? $result : 0;
     }
 
     private function getSurplusValueByCycle(User $user, Plan $plan)
@@ -109,7 +110,8 @@ class OrderController extends Controller
             $dayPrice = $dayPrice - ($dayPrice * $user->discount / 100);
         }
         $remainingDay = $user->expired_at - time();
-        return $remainingDay * $dayPrice;
+        $result = $remainingDay * $dayPrice;
+        return $result ? $result : 0;
     }
 
     public function save(OrderSave $request)