Fix: Image lightbox showing original image in synced pattern instead of overriden image

[Sourav61]

Fixed the image lightbox showing original image issue in synced pattern with overridden image

What?

Closes #64716

Why?

Previously, when opening the image lightbox, the image displayed was inconsistent—sometimes showing the original image instead of the expected overridden version. This issue caused confusion for users expecting a consistent visual experience when enlarging images.

How?

• Adjusted the logic to ensure state.currentImage.uploadedSrc is used consistently when an enlarged image is available.
• Added fallback logic to prevent empty or incorrect images from being displayed.

Testing Instructions

1. Create a synced pattern containing an image block.
2. Enable overrides for the image.
3. Insert the synced pattern on a page and replace the image with a new one.
4. Save and view the page on the front end.
5. The lightbox shows the original image from the synced pattern.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

Unlinked Accounts

The following contributors have not linked their GitHub and WordPress.org accounts: @simonwammerfors.

Contributors, please read how to link your accounts to ensure your work is properly credited in WordPress releases.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Unlinked contributors: simonwammerfors.

Co-authored-by: Sourav61 <sourav08@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.