Bugfix fatal error in PHP 8.0: Return type must be void when declared

src/Resolvers/Resolver.php

@@ -53,7 +53,7 @@ public function __get(string $property): ?string
      *
      * @return string|null
      */
-    public function __set(string $property, ?string $value): ?string
+    public function __set(string $property, ?string $value)
     {
         return $this->updateOrCreateValue($property, $value)->{HasEntityAttributeValues::$value};
     }