Merge pull request #4160 from AvaloniaUI/fixes/menuscroller-pointerleave

Close submenu when pointer leaves.

src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs

@@ -333,6 +333,10 @@ namespace Avalonia.Controls.Platform
                 {
                     item.Parent.SelectedItem = null;
                 }
+                else if (!item.IsPointerOverSubMenu)
+                {
+                    item.IsSubMenuOpen = false;
+                }
             }
         }