fix missing file image

MP-TAB/WebUserControls/BaseUserControl.cs

@@ -2,6 +2,7 @@
 using SteamWare;
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Web;
 
@@ -352,11 +353,20 @@ namespace MoonProTablet.WebUserControls
         /// <returns></returns>
         public string ImgUrlMacc(object url)
         {
+            string answ = "";
             if (string.IsNullOrEmpty(url.ToString()))
             {
-                url = "empty.png";
+                url = "Steamware.png";
             }
-            return string.Format("./images/macchine/{0}", url);
+            // verifico esistenza macchina...
+            answ = $"./images/macchine/{url}";
+            string fullPath = Server.MapPath(answ);
+            if (!File.Exists(fullPath))
+            {
+                // metto default Steamware
+                answ = "./images/macchine/Steamware.png";
+            }
+            return answ;
         }
 
         /// <summary>