Make sure DOMXPath::query did not return false

Author: Zegnat

Mf2/Parser.php

@@ -1102,7 +1102,7 @@ public function parseH(\DOMElement $e, $is_backcompat = false, $has_nested_mf =
 				);
 				foreach ($xpaths as $xpath) {
 					$url = $this->xpath->query($xpath, $e);
-					if ($url->length === 1) {
+					if ($url !== false && $url->length === 1) {
 						$return['url'][] = $this->resolveUrl($url->item(0)->getAttribute('href'));
 						break;
 					}