Fix a tiny bug

Sometimes the users may hit enter key by mistake, and the form will
close without saving entries.

shadowsocks-csharp/View/ConfigForm.cs

@@ -146,6 +146,28 @@ namespace Shadowsocks.View
 
         }
 
+        private void ConfigForm_KeyDown(object sender, KeyEventArgs e)
+        {
+            // Sometimes the users may hit enter key by mistake, and the form will close without saving entries.
+
+            if (e.KeyCode == Keys.Enter)
+            {
+                Server server = controller.GetCurrentServer();
+                if (!SaveOldSelectedServer())
+                {
+                    return;
+                }
+                if (_modifiedConfiguration.configs.Count == 0)
+                {
+                    MessageBox.Show(I18N.GetString("Please add at least one server"));
+                    return;
+                }
+                controller.SaveServers(_modifiedConfiguration.configs, _modifiedConfiguration.localPort);
+                controller.SelectServerIndex(_modifiedConfiguration.configs.IndexOf(server));
+            }
+
+        }
+
         private void ServersListBox_SelectedIndexChanged(object sender, EventArgs e)
         {
             if (!ServersListBox.CanSelect)