Content Length Missing Causing "GnuTLS recv error (-110)"

[Zortrox]

On our live server with SSL, I'm receiving an error on any event fired whenever Pusher sends a cURL request to the websocket server:
GnuTLS recv error (-110): The TLS connection was non-properly terminated.

I search for hours and eventually saw that in some versions of cURL that use GnuTLS, if an explicit "Content-Length" header isn't present, cURL outputs an error when the server closes the connection.

Server info:

PHP: 7.4.23
cURL: 7.68.0
GnuTLS: 3.6.13

Example PHP cURL code that would cause this error:

$full_url = 'https://api.example.com:6001/apps/{{appname}}/events?auth_key={{auth_key}}&auth_signature={{auth_signature}}&auth_timestamp=1632939475&auth_version=1.0&body_md5={{body_md5}}';

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $full_url);
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_HTTPHEADER, array(
    'Content-type: application/json'
));

curl_setopt($ch, CURLOPT_POSTFIELDS, '{}');

$response = array();
$response['body'] = curl_exec($ch);
$response['status'] = curl_getinfo($ch, CURLINFO_HTTP_CODE);

var_dump($response, curl_error($ch));

I'm submitting a pull request now that should fix this issue.