Dont use empty() (#8)

* Dont use `empty()`

* cs

Author: Nyholm

src/EntityExistValidator.php

@@ -23,14 +23,14 @@ public function __construct(EntityManagerInterface $entityManager)
 
     public function validate($value, Constraint $constraint): void
     {
-        if (empty($value)) {
-            return;
-        }
-
         if (!$constraint instanceof EntityExist) {
             throw new \LogicException(\sprintf('You can only pass %s constraint to this validator.', EntityExist::class));
         }
 
+        if (null === $value || '' === $value) {
+            return;
+        }
+
         if (empty($constraint->entity)) {
             throw new \LogicException(\sprintf('Must set "entity" on "%s" validator', EntityExist::class));
         }