fix(kawa_h1): give response stream instead of request stream

* Fix an index out of bound issue
* We are in the request parsing stream, so we should diagnostic
  the response is something goes wrong

Signed-off-by: Florentin Dubois <florentin.dubois@clever-cloud.com>

lib/src/protocol/kawa_h1/mod.rs

@@ -831,7 +831,7 @@ impl<Front: SocketHandler, L: ListenerHandler + L7ListenerHandler> Http<Front, L
             if response_stream.consumed {
                 return SessionResult::Close;
             } else {
-                let (message, details) = diagnostic_400_502(marker, kind, &self.request_stream);
+                let (message, details) = diagnostic_400_502(marker, kind, response_stream);
                 self.set_answer(DefaultAnswer::Answer502 {
                     phase: marker,
                     details,