Fixed path for finalization errors when using a prototype

Author: stof

src/Symfony/Component/Config/Definition/ArrayNode.php

@@ -293,6 +293,7 @@ protected function finalizeValue($value)
 
  if (null !== $this->prototype) {
  foreach ($value as $k => $v) {
+ $this->prototype->setName($k);
  try {
  $value[$k] = $this->prototype->finalize($v);
  } catch (UnsetKeyException $unset) {