httpcompression middleware: empty body in bytes, not str

scrapy/downloadermiddlewares/httpcompression.py

@@ -123,7 +123,7 @@ def _decode(self, body: bytes, encoding: bytes) -> bytes:
  if b"br" in ACCEPTED_ENCODINGS:
  body = brotli.decompress(body)
  else:
- body = ""
+ body = bytes()
  logger.warning(
  "Brotli encoding received. "
  "Cannot decompress the body as Brotli is not installed."