Merge branch '5.3' into 5.4

* 5.3:
  [Ldap] Avoid calling the deprecated getUsername()
  Report the correct package in the deprecation message
  Wrapping exception js in Sfjs check and also loading base_js Sfjs if needed
  Fix PHP 8.1 deprecations
  Add missing deprecation entry
  [VarDumper] Don't pass null to parse_url()
  Invalid copy-paste fix

Slugger/AsciiSlugger.php

@@ -103,7 +103,7 @@ public function slug(string $string, string $separator = '-', string $locale = n
         $locale = $locale ?? $this->defaultLocale;
 
         $transliterator = [];
-        if ('de' === $locale || 0 === strpos($locale, 'de_')) {
+        if ($locale && ('de' === $locale || 0 === strpos($locale, 'de_'))) {
             // Use the shortcut for German in UnicodeString::ascii() if possible (faster and no requirement on intl)
             $transliterator = ['de-ASCII'];
         } elseif (\function_exists('transliterator_transliterate') && $locale) {