fix optimisation

src/mimefactory.rs

@@ -346,12 +346,7 @@ impl<'a, 'b> MimeFactory<'a, 'b> {
                         32,
                         self.context,
                     );
-                    let mut lines = raw.lines();
                     let raw_subject = raw.lines().next().unwrap_or_default();
-                        line
-                    } else {
-                        ""
-                    };
                     format!("Chat: {}", raw_subject)
                 }
             }