Fix build error.

fis/Program.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Globalization;
 using Avalonia;
 using Xilium.CefGlue;
@@ -7,12 +8,12 @@ using fis.Log;
 
 namespace fis
 {
-	[STAThread]
     class Program
     {
         // Initialization code. Don't use any Avalonia, third-party APIs or any
         // SynchronizationContext-reliant code before AppMain is called: things aren't initialized
         // yet and stuff might break.
+        [STAThread]
         public static void Main(string[] args)
         {
             Logger.Init(new DefaultLogEngine());