Merge branch '5.2' into 5.x

* 5.2:
  [Finder] Fix gitignore regex build with "**"
  Fixed deprecation warnings about passing null as parameter
  [Security] Keep Bulgarian wording consistent across all texts.
  Migrate configuration file for PHP CS Fixer 2.19/3.0
  [Form] Replace broken ServerParams mock
  [Mailer] Fix SES API call with UTF-8 Addresses

Author: fabpot

AbstractUriElement.php

@@ -47,7 +47,7 @@ public function __construct(\DOMElement $node, string $currentUri = null, ?strin
         $this->currentUri = $currentUri;
 
         $elementUriIsRelative = null === parse_url(trim($this->getRawUri()), \PHP_URL_SCHEME);
-        $baseUriIsAbsolute = \in_array(strtolower(substr($this->currentUri, 0, 4)), ['http', 'file']);
+        $baseUriIsAbsolute = null !== $this->currentUri && \in_array(strtolower(substr($this->currentUri, 0, 4)), ['http', 'file']);
         if ($elementUriIsRelative && !$baseUriIsAbsolute) {
             throw new \InvalidArgumentException(sprintf('The URL of the element is relative, so you must define its base URI passing an absolute URL to the constructor of the "%s" class ("%s" was passed).', __CLASS__, $this->currentUri));
         }