NavigationView Bug: Unexpected separators and menu item jumping behavior

[SDSC0623]

Describe the bug

In the latest release (v4.0.3), the NavigationView component introduced two visual issues:
1. ​​Unexpected separators:​​

• Added separator lines appear between Header/Menu and Menu/Footer sections with no visibility control property.
• The separator above Footer persists even when Footer is empty.

2. ​​Menu item jumping:​​

• Menu items shift vertically (±3px) when expanding/collapsing the navigation pane.

To Reproduce

4.0.3:

4.0.2:

You can see two distinct separator in the screenshot of version 4.0.3.

4.0.3:

You can see that the separator above are clearly not at the same height when it is collapsed and expanded.

Expected behavior

1. Separators should be controllable via new property (e.g. HeaderSeparatorVisibility/FooterSeparatorVisibility)
2. Both separators should auto-hide when adjacent elements are null/empty
3. Menu items should maintain stable vertical position during pane transitions

Screenshots

No response

OS version

Windows 11 23H2 Build 22631.4602

.NET version

8.0.403

WPF-UI NuGet version

4.0.3

Additional context

No response