Add guard against missing post

Author: chriszarate

src/parser/block-additions/core-block.php

@@ -83,6 +83,11 @@ public static function get_inner_blocks( array $inner_blocks, string $block_name
 		// ContentParser->parse() to avoid calling telemetry and filters again.
 		$parser = new ContentParser();
 		$post   = get_post( $parsed_block['attrs']['ref'] );
+
+		if ( ! $post instanceof \WP_Post ) {
+			return [];
+		}
+
 		$blocks = parse_blocks( $post->post_content );
 
 		return array_map( function ( array $block ) use ( $parser, $context, $post_id ): WP_Block {

tests/parser/test-synced-patterns.php

@@ -165,6 +165,28 @@ public function test_multiple_synced_patterns() {
 		$this->assertEquals( $expected_blocks, $blocks['blocks'], sprintf( 'Blocks not equal: %s', wp_json_encode( $blocks['blocks'] ) ) );
 	}
 
+	/* Missing synced pattern */
+
+	public function test_missing_synced_pattern() {
+		$html = sprintf( '<!-- wp:block {"ref":%d} /-->', -1 );
+
+		$expected_blocks = [
+			[
+				'name'        => 'core/block',
+				'attributes'  => [
+					'ref' => -1,
+				],
+				// inner_blocks is omitted when empty for backwards compatibility with earlier release
+			],
+		];
+
+		$content_parser = new ContentParser( $this->get_block_registry() );
+		$blocks         = $content_parser->parse( $html );
+
+		$this->assertArrayHasKey( 'blocks', $blocks, sprintf( 'Unexpected parser output: %s', wp_json_encode( $blocks ) ) );
+		$this->assertEquals( $expected_blocks, $blocks['blocks'], sprintf( 'Blocks not equal: %s', wp_json_encode( $blocks['blocks'] ) ) );
+	}
+
 	/* Synced pattern with override */
 
 	public function test_synced_pattern_with_override() {