Fix: `useEditorBlocks` hook always returns an array (#41874)

* fix: useEditorBlocks hook always returns an array

* Add changefile(s) from automation for the following project(s): woocommerce

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Co-authored-by: github-actions <github-actions@github.com>

plugins/woocommerce-admin/client/customize-store/assembler-hub/hooks/use-editor-blocks.ts

@@ -34,10 +34,10 @@ export const useEditorBlocks = (): [
 
 	// @ts-ignore Types are not up to date.
 	const [ blocks, onInput, onChange ]: [
-		BlockInstance[],
+		BlockInstance[] | undefined,
 		ChangeHandler,
 		ChangeHandler
 	] = useEntityBlockEditor( 'postType', templateType );
 
-	return [ blocks, onInput, onChange ];
+	return [ blocks ?? [], onInput, onChange ];
 };

plugins/woocommerce/changelog/41874-41873-cys-the-editor-has-encountered-an-unexpected-error-when-modifying-pre-generated-site

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fix
+
+Fix: `useEditorBlocks` hook always returns an array.