Uninitialised fields when OpenSSL is enabled

[zhiayang]

The socket destructor unconditionally calls this->close(), and that checks:

if(pSSL && pContext) {
    SSL_xxx(...)
}

Unfortunately these fields are pointers that aren't initialised to a value unless you connect() the socket first. So, destructing an unconnected socket with SSL enabled will most likely result in trying to pass garbage pointers to openSSL and causing a crash.

A simple fix is just to set them to nullptr either at the declaration site or in the constructor. They also need to be set to zero when moved from, similar to this getaddrinfo_results fix.