fix error with post_text extension

Form/Extension/PostTextNumberExtension.php

@@ -19,6 +19,8 @@
 
 namespace Chill\CustomFieldsBundle\Form\Extension;
 
+use Symfony\Component\Form\Extension\Core\Type\NumberType;
+
 /**
  * This class add the PostTextExtension to number fields
  *
@@ -28,7 +30,7 @@ class PostTextNumberExtension extends PostTextExtension
 {
     public function getExtendedType()
     {
-        return PostTextNumberExtension::class;
+        return NumberType::class;
     }
 
 }