Meta fields undefined after reuse commit

[iandunn]

After bfbcc92 (#19498, #15114), fetching a REST API field like meta._wp_page_template no longer works.

Reproduction Steps

1. Edit a page and add a template to it. You may need to switch to a theme that has templates, like TwentyTwenty.
2. Make that meta field available in the REST API. Add this to an mu-plugin:

   register_post_meta(
   	'page',
   	'_wp_page_template',
   	array(
   		'show_in_rest' => true,
   	)
   );

3. Call the following from any block's Edit function:

   function test() {
   	const args = {
   		_fields: [
   			'id',
   			'slug',
   			'meta._wp_page_template',
   		],
   	};
   
   	const test = useSelect(
   		( select ) => {
   			return select( 'core' ).getEntityRecords( 'postType', 'page', args );
   		},
   		[]
   	);
   
   	console.log( null !== test ? test[ 0 ][ 'meta' ] : test );
   }

4. Add that block to a post/page.
5. git checkout bfbcc92a207dd6813967bf1eff667f0a1e1bcc56~1 and reload. You should see the meta data available in the console.
6. git checkout bfbcc92a207dd6813967bf1eff667f0a1e1bcc56, and reload. You should only see null in the console.

cc @youknowriad , @aduth , @mcsf