[Doctrine] fixed Doctrine guesser when the object is a proxy and not an original entity instance

After this patch, the guesser is run for regular entity instances and proxy instances.

src/Symfony/Bridge/Doctrine/Form/DoctrineOrmTypeGuesser.php

@@ -16,6 +16,7 @@ use Symfony\Component\Form\Guess\Guess;
 use Symfony\Component\Form\Guess\TypeGuess;
 use Symfony\Component\Form\Guess\ValueGuess;
 use Symfony\Bridge\Doctrine\RegistryInterface;
+use Doctrine\ORM\Mapping\MappingException;
 
 class DoctrineOrmTypeGuesser implements FormTypeGuesserInterface
 {
@@ -122,8 +123,10 @@ class DoctrineOrmTypeGuesser implements FormTypeGuesserInterface
 
         $this->cache[$class] = null;
         foreach ($this->registry->getEntityManagers() as $name => $em) {
-            if (!$em->getConfiguration()->getMetadataDriverImpl()->isTransient($class)) {
+            try {
                 return $this->cache[$class] = array($em->getClassMetadata($class), $name);
+            } catch (MappingException $e) {
+                // not an entity or mapped super class
             }
         }
     }