Ticket #39827: 39827.diff

src/wp-includes/canonical.php

@@ -388 +388 @@
         else
                 unset($redirect['port']);
 
-        // trailing /index.php
-        $redirect['path'] = preg_replace('|/' . preg_quote( $wp_rewrite->index, '|' ) . '/*?$|', '/', $redirect['path']);
+        // Redirect can be missing path key caused by failed (and suppressed) parse_url calls.
+        if ( empty( $redirect['path'] ) ) {
+                $redirect['path'] = '';
+        }
+
+        // We don't need to initiate a regular expression call if the path is empty.
+        if ( ! empty( $redirect['path'] ) ) {
+                // trailing /index.php
+                $redirect['path'] = preg_replace( '|/' . preg_quote( $wp_rewrite->index, '|' ) . '/*?$|', '/', $redirect['path'] );
+        }
 
         $punctuation_pattern = implode( '|', array_map( 'preg_quote', array(
                 ' ', '%20',       // space