clippy fix

Author: link2xt

src/tokio/bufread/generic/decoder.rs

@@ -95,7 +95,7 @@ impl<R: AsyncBufRead, D: Decode> Decoder<R, D> {
                             let done = this.decoder.decode(&mut input, output)?;
                             let len = input.written().len();
                             this.reader.as_mut().consume(len);
-                            if output.written().len() == 0 {
+                            if output.written().is_empty() {
                                 *this.multiple_members = false;
                                 State::Flushing
                             } else if done {