reason from output:
4 Query: SelectQuery .
    5      | SelectQuery . LIMIT INTEGER
   17 UnionQuery: SelectQuery .
    LIMIT  shift, and go to state 16
    $end      reduce using rule 4 (Query)
    $end      [reduce using rule 17 (UnionQuery)]
    LIMIT     [reduce using rule 17 (UnionQuery)]
    $default  reduce using rule 4 (Query)
solution: add '('')' around state 17