Fix buffer empty when reading numeric types

[danylaporte]

Fix invalid protocol token crash caused by the following request:

use futures::Future;
use futures_state_stream::StateStream;
use tiberius::{
    ty::{Guid, Numeric},
    SqlConnection,
};
use tokio::executor::current_thread;

fn main() {
    // 1: Same as in the example above
    let conn_str = "server=tcp:localhost\\SQL2017;database=master;integratedsecurity=sspi;trustservercertificate=true";
    let mut i = 0;

    let future = SqlConnection::connect(conn_str).and_then(|conn| {
        conn.simple_query(
            r#"
            with cte as (
	SELECT CAST(999999999.99 as DECIMAL(28, 12)) c
	UNION ALL
	SELECT  CAST(999999999.99 as DECIMAL(28, 12)) c FROM cte
)
SELECT TOP 50 * FROM cte
UNION ALL 
SELECT TOP 50 * FROM cte
UNION ALL 
SELECT TOP 50 * FROM cte
UNION ALL 
SELECT TOP 50 * FROM cte
UNION ALL 
SELECT TOP 50 * FROM cte
UNION ALL 
SELECT TOP 50 * FROM cte
UNION ALL 
SELECT TOP 50 * FROM cte
UNION ALL 
SELECT TOP 50 * FROM cte"#,
        )
        .for_each(|r| {
            let n = r.get::<_, Numeric>(0);
            println!("{}: {:?}: {}", i, n, n.scale());

            i += 1;
            Ok(())
        })
    });

    current_thread::block_on_all(future).unwrap();
}

[steffengy]

Thanks, that seems right.
Could you add this as test aswell?

[danylaporte]

Test added! :)