fix

src/Readability.php

@@ -1480,6 +1480,7 @@ class Readability implements LoggerAwareInterface
         $childNodes = iterator_to_array($node->childNodes);
         $children = array_filter($childNodes, fn ($childNode) => $childNode instanceof \DOMElement);
 
+        $children = array_values($children);
         // There should be exactly 1 element child with given tag
         if (1 !== \count($children) || $children[0]->nodeName !== $tag) {
             return false;