proto_wss: proper cleanup wss connection in case of tls error

When TLS domain is not found, or the SSL context cannot be created, make
sure the connection does not keep an hanging `proto_data` that will be
later double-freed by the cleanup routine.

Credits go to Jonathan Hulme (@digipigeon) for reporting this.

Close #2123

modules/proto_wss/proto_wss.c

@@ -288,6 +288,7 @@ static int wss_conn_init(struct tcp_connection* c)
 
 	ret = tls_conn_init(c, &tls_mgm_api);
 	if (ret < 0) {
+		c->proto_data = NULL;
 		LM_ERR("Cannot initiate the conn\n");
 		shm_free(d);
 	}