Declare type of the $data private member to array|null, to avoid warnings by PHP linters.

Author: patacra

src/Supporting/FileMakerRelation.php

@@ -21,7 +21,7 @@
 class FileMakerRelation implements Iterator
 {
     /**
-     * @var null
+     * @var null|array
      * @ignore
      */
     private $data = null;