fix issue with closing bracket following a null token in Tokenizer

Author: joonlabs

src/Parser/Tokenizer.php

@@ -78,7 +78,7 @@ class Tokenizer
 
         // --------------------------------------------
         // Null
-        ['/^(null)(?![_A-Za-z:\)])/', "NULL"],
+        ['/^(null)(?![_A-Za-z:])/', "NULL"],
 
         // --------------------------------------------
         // Names