SET statement not properly parsed or build

```php
$sql    = 'SET SESSION   sql_mode = \'TRADITIONAL\'';
$parser = new Parser($sql);
$s2     = $parser->statements[0]->build();
// $s2 is **missing whitespace** in **SESSIONsql_mode**
//SET  SESSIONsql_mode = 'TRADITIONAL'

//PHP 7.1.18
//"name": "phpmyadmin/sql-parser",
//"version": "5.0.0",
```