Fix: Prevent Tiled Gallery crash and add changelog entry (#49606)

[Tejas-Raj01]

Fixes #49606

Proposed changes

• Fixes an editor crash that occurs when transforming a Gallery block back to a Tiled Gallery. The fix ensures the images attribute is recovered from innerBlocks when the top-level images attribute is empty or undefined.

Related product discussion/links

• Issue: Tiled Gallery: editor crashes converting Gallery → Tiled Gallery after a Tiled→Gallery round-trip ("Cannot read properties of undefined (reading 'filter')") #49606

Does this pull request change what data or activity we track or use?

• No, this PR does not change any data tracking or activity collection.

Testing instructions

• Go to any Post or Page in the Block Editor.
• Add a standard "Gallery" block and upload/select multiple images.
• Transform this "Gallery" block into a "Tiled Gallery" block using the block toolbar transformation option.
• Before this fix: The editor would trigger a crash/error due to missing images in the block attributes.
• After this fix: The Tiled Gallery block should render successfully by recovering the image data from the block's innerBlocks.

[github-actions]

Thank you for your PR!

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• ✅ Add testing instructions.
  
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• ✅ Add changelog entries to affected projects
  

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Jetpack plugin:

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