Async client segfaults if ssl options are not set

[Altair-Bueno]

Current behavior

Segfault for MQTT over TLS/TCP if SslOptions are unset.

Expected behavior

Memory safety guarantees. No invalid access.

Sample code

use paho_mqtt::async_client::AsyncClient;
use paho_mqtt::ssl_options;

#[tokio::main]
async fn main() {
    let client = paho_mqtt::CreateOptionsBuilder::new().finalize();
    let client = AsyncClient::new(client).unwrap();

    #[allow(unused)]
    let ssl_options = ssl_options::SslOptionsBuilder::new().finalize();
    let connect = paho_mqtt::ConnectOptionsBuilder::new()
        .server_uris(&["mqtts://test.mosquitto.org:8883"])
        //.ssl_options(ssl_options)
        .finalize();
    client.connect(connect).await.unwrap();
}

paho-mqtt-segfault-no-ssl-options.zip