set test cookie if it is not empty

src/test.rs

@@ -172,10 +172,12 @@ impl TestRequest {
             let value = percent_encode(c.value().as_bytes(), USERINFO_ENCODE_SET);
             let _ = write!(&mut cookie, "; {}={}", name, value);
         }
+        if !cookie.is_empty() {
             head.headers.insert(
                 header::COOKIE,
                 HeaderValue::from_str(&cookie.as_str()[2..]).unwrap(),
             );
+        }
 
         req
     }