RichText: don't apply input transform when there's no onReplace

[jsnajdr]

Fixes a crash when a RichText field wants to apply an input transform, but there is no onReplace handler that would execute the transform, i.e., replace the current block with another one.

Steps to reproduce:

1. Create a core/pullquote block that has a field with text, but no ability to contain inner blocks. Or a locked core/paragraph, with locked removal.
2. Type --- inside. This would normally convert the block to a separator, but in these cases the new block can't be created.
3. There is a crash:

The fix is to guard the transform logic on onReplace and don't attempt transforms. The inputRule function in the same file already guards on onReplace when handling the prefix transforms.

This bug was reported in WP.com automated JS error reporting.

[github-actions]

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Co-authored-by: jsnajdr <jsnajdr@git.wordpress.org>
Co-authored-by: aduth <aduth@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>

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[github-actions]

Size Change: +9 B (0%)

Total Size: 7.76 MB

📦 View Changed

Filename	Size	Change
build/scripts/block-editor/index.min.js	428 kB	+9 B (0%)

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[aduth]

This makes sense 👍 Though my static typing brain wonders what the expected shape of onReplace should be, and if it's reasonable to expect it should always be a function that locking blocks could pass as a noop rather than as undefined.

[Mamaduka]

Thanks, @jsnajdr!

[Mamaduka]

@aduth, the RichText relies on a similar if ( onReplace ) check in a couple of places, which probably would require larger refactoring than just swapping with noop.

P.S. I think we had similar conversation on another Jarda's PRs 😄

[jsnajdr]

what the expected shape of onReplace should be

By not passing onReplace we signal to RichText that this operation is not available, and that it shouldn't attempt it. If onReplace was noop, then RichText would think it did the --- to core/separator transform, but in fact it wouldn't happen.