Error found in HttpRequestParser:parse
PHP version: 7.4

When sending HTTP request headers to `Telnet`,
If `'/'` is missing from `GET HTTP/1.1`
An error has occurred.

An error occurs when creating `GuzzleHttp\Psr7\Request` instance in `Message:parseRequest` if the version parameter is null
```
PHP Fatal error:  Uncaught TypeError: GuzzleHttp\Psr7\Request::__construct(): Argument #5 ($version) must be of type string, null given, ...
/guzzlehttp/psr7/src/Request.php:35
```

From `HttpRequestParser:parse`
Error parsing http header to `guzzlehttp/psr7/Message` library.

It seems that the header verification process is necessary before parsing.