🐛 bug: don't send Content-Length to relay if status code is 304 Not Modified

Thanks to Nginx for noticing this

crates/ptth_server/src/lib.rs

@@ -97,9 +97,12 @@ async fn handle_one_req (
 	.header (ptth_core::PTTH_MAGIC_HEADER, base64::encode (rmp_serde::to_vec (&response.parts).map_err (ServerError::MessagePackEncodeResponse)?))
 	.header ("X-PTTH-SERVER-NAME", &state.config.name);
 	
-	if let Some (length) = response.content_length {
-		resp_req = resp_req.header ("Content-Length", length.to_string ());
+	if response.parts.status_code != ptth_core::http_serde::StatusCode::NotModified {
+		if let Some (length) = response.content_length {
+			resp_req = resp_req.header ("Content-Length", length.to_string ());
+		}
 	}
+	
 	if let Some (mut body) = response.body {
 		if state.config.throttle_upload {
 			// Spawn another task to throttle the chunks