Issue #3388010: PHP8.1 compatibility

modules/providers/service_container_symfony/lib/Symfony/Component/Yaml/Inline.php

@@ -46,7 +46,7 @@ class Inline
         self::$objectSupport = $objectSupport;
         self::$objectForMap = $objectForMap;
 
-        $value = trim($value);
+        $value = trim($value ?? '');
 
         if (0 == strlen($value)) {
             return '';