Embeds: In switched state, restore previous state if no post ID is found.

Fixes #40673.

git-svn-id: https://develop.svn.wordpress.org/trunk@41634 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/embed.php

@@ -1106,6 +1106,10 @@ function wp_filter_pre_oembed_result( $result, $url, $args ) {
 	$post_id = apply_filters( 'oembed_request_post_id', $post_id, $url );
 
 	if ( ! $post_id ) {
+		if ( $switched_blog ) {
+			restore_current_blog();
+		}
+
 		return $result;
 	}