validateOptionTypes checking existence of key rather than value

Author: EvanK

OptionsResolver.php

@@ -312,7 +312,7 @@ private function validateOptionValues(array $options)
     private function validateOptionTypes(array $options)
     {
         foreach ($this->allowedTypes as $option => $allowedTypes) {
-            if (!isset($options[$option])) {
+            if (!array_key_exists($option, $options)) {
                 continue;
             }