Navigation Link: Use optional chaining for linkUIref

[yogeshbhutkar]

Fixes: #67712

What?

An optional chaining for property access was introduced to access the properties of linkUIref to prevent the error described in the issue.

Why?

The absence of this optional chaining caused Uncaught TypeError and this PR is a fix in response to it.

How?

This PR fixes the issue by implementing optional chaining to resolve the error condition.

Testing Instructions

1. Navigate to Patterns → Header, and select any pattern containing the Navigation Core Block.
2. Select the Navigation Core Block and click the "plus" button.
3. Click "+ Add block," then select "Browse All" to open the sidebar with available blocks.
4. Click on any block in the sidebar to add it to the Navigation Core Block.
5. Observe that there's no error in the console.

Screencast

Before:

Screen.Recording.2024-12-09.at.9.59.09.AM.mov

After:

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Co-authored-by: yogeshbhutkar <yogeshbhutkar@git.wordpress.org>
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[jeryj]

I've confirmed there's no more Uncaught TypeError when adding a block via this method. However, there may be a deeper issue here that the link ui should not be getting mounted at all after a block is added.

[Mamaduka]

@yogeshbhutkar, closing this in favor of #67760, which fixes the root cause of the issue.