Issue #3418766 by jay.silverman: Deprecated function: urldecode()

Closes #3418766

src/Form/RegexRedirectForm.php

@@ -146,7 +146,7 @@ class RegexRedirectForm extends ContentEntityForm {
    * @throws MatchingRouteNotFoundException
    */
   protected function setDefaultOptions(RegexRedirect $redirect) {
-    $source_url = urldecode($this->getRequest()->get('source'));
+    $source_url = urldecode($this->getRequest()->get('source') ?? '');
     if (!empty($source_url)) {
       $redirect->setSource($source_url);
     }
@@ -215,7 +215,7 @@ class RegexRedirectForm extends ContentEntityForm {
     $source_regex = $delimiter . trim($source_path) . $delimiter;
     $redirect_regex = str_replace('internal:', '', $redirect_uri);
 
-    if (preg_match($source_regex, NULL) === FALSE) {
+    if (preg_match($source_regex, '') === FALSE) {
       $form_state->setErrorByName('regex_redirect_source', $this->t('The regex redirect source must be a regex pattern.'));
     }
     if (preg_match('/<(.*?)>/', $redirect_regex) !== 1) {