Ticket #47005: 47005.patch

src/wp-includes/load.php

@@ -13 +13 @@
  * @return string The HTTP protocol. Default: HTTP/1.0.
  */
 function wp_get_server_protocol() {
-        $protocol = $_SERVER['SERVER_PROTOCOL'];
+        $protocol = isset( $_SERVER['SERVER_PROTOCOL'] ) ? $_SERVER['SERVER_PROTOCOL'] : '';
         if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0' ) ) ) {
                 $protocol = 'HTTP/1.0';
         }