Fix parsing invalid href

Author: grandeljay

src/Detectors/Languages.php

@@ -17,7 +17,7 @@ public function detect(): array
             $language = $node->getAttribute('hreflang');
             $href = $node->getAttribute('href');
 
-            if (!$language || !$href) {
+            if (isEmpty()) {
                 continue;
             }
 
@@ -26,4 +26,13 @@ public function detect(): array
 
         return $languages;
     }
+
+    private function isEmpty($value): boolval
+    {
+        $skipValues = array(
+            'undefined',
+        );
+
+        return empty($value) || in_array($value, $skipValues);
+    }
 }