From 7b0a1839203af6691bb3af9de4c78689e966dda2 Mon Sep 17 00:00:00 2001
From: prosalov <mnpropro@gmail.com>
Date: Fri, 11 Dec 2020 21:51:28 +0000
Subject: [PATCH] [DomCrawler] Fix null namespace issue in Crawler

---
 src/Symfony/Component/DomCrawler/Crawler.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Symfony/Component/DomCrawler/Crawler.php b/src/Symfony/Component/DomCrawler/Crawler.php
index 2b4e1dfaaaad9..fe00fa3fb8238 100644
--- a/src/Symfony/Component/DomCrawler/Crawler.php
+++ b/src/Symfony/Component/DomCrawler/Crawler.php
@@ -1194,11 +1194,11 @@ private function createDOMXPath(\DOMDocument $document, array $prefixes = []): \
      */
     private function discoverNamespace(\DOMXPath $domxpath, string $prefix): ?string
     {
-        if (isset($this->namespaces[$prefix])) {
+        if (\array_key_exists($prefix, $this->namespaces)) {
             return $this->namespaces[$prefix];
         }
 
-        if (isset($this->cachedNamespaces[$prefix])) {
+        if ($this->cachedNamespaces->offsetExists($prefix)) {
             return $this->cachedNamespaces[$prefix];
         }