Its possible to crash editor by calling `selectBlock` on a non-existent clientId about gutenberg

[Mamaduka]

The BlockSwitcher checks the validity of blocks before rendering transformation options. It was introduced initially to solve a similar error - #28122.

I'm not against updating the getBlocksByClientId, but we should examine its usage in the code base in case any consumer relies on current behavior.

gutenberg/packages/block-editor/src/components/block-switcher/index.js

Lines 182 to 184 in 599f336

	if ( ! _blocks.length || _blocks.some( ( block ) => ! block ) ) {
	return { invalidBlocks: true };
	}

[t-hamano]

Thanks for the report.

I also think that it should prevent the block editor from crashing, and that returning an array with null when the getBlocksByClientId parameter contains an invalid ID is not the expected behavior.

The getBlocksByClientId is expected to return an array of type WPBlock, but looking at the type below, null should not be allowed.

gutenberg/packages/blocks/src/api/parser/index.js

Lines 42 to 50 in 908e3ed

	* @typedef WPBlock
	*
	* @property {string} name Block name
	* @property {Object} attributes Block raw or comment attributes.
	* @property {WPBlock[]} innerBlocks Inner Blocks.
	* @property {string} originalContent Original content of the block before validation fixes.
	* @property {boolean} isValid Whether the block is valid.
	* @property {Object[]} validationIssues Validation issues.
	* @property {WPRawBlock} [__unstableBlockSource] Un-processed original copy of block if created through parser.

[artpi]

For now I opened a PR with a spot remedy.

[t-hamano]

Fixed by #59410