fix: normalize empty reason phrase to None in asyncio transport

The asyncio HTTP client was reporting an empty reason phrase as an
empty string instead of None, inconsistent with the requests and httpx
transports which normalize empty reason phrases to None.

Changed the one-liner to coerce empty string to None so that
Response.reason is consistent across all adapters.

Author: Gautam Kumar

packages/dexpace-sdk-http-stdlib/src/dexpace/sdk/http/stdlib/asyncio_http_client.py

@@ -232,7 +232,7 @@ async def _read(
             raise ServiceResponseError(f"Malformed status line: {status_line!r}")
         protocol = _PROTOCOL_BY_VERSION.get(parts[0], Protocol.HTTP_1_1)
         status = _parse_status(parts[1])
-        reason = parts[2] if len(parts) > 2 else None
+        reason = (parts[2] or None) if len(parts) > 2 else None
         headers = await self._read_headers(reader)
         body_bytes = await self._read_body(reader, headers)
         return AsyncResponse(