Map block: Prevent PHP fatal when content is empty (#41583)

* Return early if content is empty

* Add comment

* Add changelog

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/13180555895

Upstream-Ref: Automattic/jetpack@c02cec5

CHANGELOG.md

@@ -29,6 +29,7 @@ This is an alpha version! The changes listed here are not final.
 - Jetpack SEO: assistant option bubbles border design
 - Jetpack SEO: fix state inconsistencies, change effects and use global isBusy suspense flag
 - Jetpack Sync: Fixed extracting UTF-8 characters from image alt-text
+- Map block: Catch error if content is empty.
 - Reader: Update url from /read to /reader
 - Reset to-test.md for Jetpack 14.4 release cycle.
 - Sync: Full-sync chunking logic dynamic for Woo modules

extensions/blocks/map/map.php

@@ -154,6 +154,11 @@ function render_single_block_page() {
 	/** This filter is already documented in core/wp-includes/post-template.php */
 	$content = apply_filters( 'the_content', $post->post_content );
 
+	// Return early if empty to prevent DOMDocument::loadHTML fatal.
+	if ( empty( $content ) ) {
+		return;
+	}
+
 	/* Suppress warnings */
 	libxml_use_internal_errors( true );
 	@$post_html->loadHTML( $content ); // phpcs:ignore WordPress.PHP.NoSilencedErrors.Discouraged