Merge pull request #1127 from WouterJ/fix_deprecation_call

Fixed deprecation call

Datagrid/Datagrid.php

@@ -100,7 +100,7 @@ class Datagrid implements DatagridInterface
         }
 
         $this->formBuilder->add('_sort_by', 'hidden');
-        $this->formBuilder->get('_sort_by')->appendClientTransformer(new CallbackTransformer(
+        $this->formBuilder->get('_sort_by')->addViewTransformer(new CallbackTransformer(
             function($value) { return $value; },
             function($value) { return $value instanceof FieldDescriptionInterface ? $value->getName() : $value; }
         ));