Merge pull request #722 from irihitech/focus

Fix IPBox and MultiComboBox focus style

src/Ursa/Controls/IPv4Box/IPv4Box.cs

@@ -307,6 +307,7 @@ public class IPv4Box: TemplatedControl
 
     protected override void OnLostFocus(RoutedEventArgs e)
     {
+        base.OnLostFocus(e);
         foreach (var pre in _presenters)
         {
             pre?.HideCaret();