Query: Remove nextpage block delimiters when setting up global post data.

`WP_Query::setup_postdata()` splits the post up by `<!--nextpage-->`, which causes invalid block data to be contained in the post content.

This change removes the `<!-- wp:nextpage -->` and `<!-- /wp:nextpage -->`, as well.

Props pento, youknowriad, azaozz, noisysocks.

Merges [43940] into trunk.

See #45401.
Built from https://develop.svn.wordpress.org/trunk@44276


git-svn-id: http://core.svn.wordpress.org/trunk@44106 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-query.php

@@ -4164,6 +4164,10 @@ class WP_Query {
 			$content = str_replace( "\n<!--nextpage-->", '<!--nextpage-->', $content );
 			$content = str_replace( "<!--nextpage-->\n", '<!--nextpage-->', $content );
 
+			// Remove the nextpage block delimiters, to avoid invalid block structures in the split content.
+			$content = str_replace( '<!-- wp:nextpage -->', '', $content );
+			$content = str_replace( '<!-- /wp:nextpage -->', '', $content );
+
 			// Ignore nextpage at the beginning of the content.
 			if ( 0 === strpos( $content, '<!--nextpage-->' ) ) {
 				$content = substr( $content, 15 );

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-alpha-44275';
+$wp_version = '5.1-alpha-44276';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.