[Form] Fixed EntityChoiceFieldTest

src/Symfony/Component/Form/ValueTransformer/EntityToIdTransformer.php

@@ -33,7 +33,7 @@ class EntityToIdTransformer implements ValueTransformerInterface
      */
     public function transform($entity)
     {
-        if (null === $entity) {
+        if (null === $entity || '' === $entity) {
             return '';
         }
 
@@ -60,7 +60,7 @@ class EntityToIdTransformer implements ValueTransformerInterface
      */
     public function reverseTransform($key)
     {
-        if ('' === $key) {
+        if ('' === $key || null === $key) {
             return null;
         }
 

tests/Symfony/Tests/Component/Form/EntityChoiceFieldTest.php

@@ -170,7 +170,7 @@ class EntityChoiceFieldTest extends DoctrineOrmTestCase
         $field->setData(null);
 
         $this->assertEquals(new ArrayCollection(), $field->getData());
-        $this->assertEquals('', $field->getDisplayedData());
+        $this->assertEquals(array(), $field->getDisplayedData());
     }
 
     public function testSubmitSingleExpanded_null()