DuckDB::Result can't read BIT column value

[suketa]

irb(main):002> db = DuckDB::Database.open
irb(main):003> con = db.connect
irb(main):004> con.execute('CREATE TABLE t (val BIT);')
irb(main):005> con.execute("INSERT INTO t VALUES ('1'::BIT);")
irb(main):006> r = con.execute("SELECT * FROM t;")
irb(main):007> r.to_a
/home/suke/mywork/ruby-duckdb/lib/duckdb/result.rb:83: warning: Unknown type 29
=> [[nil]]

[suketa]

fixed by #672