channel.c: remove logically dead code, host cannot be NULL here

... host cannot be NULL in line 525, because it is always
valid (e.g. at least set to "0.0.0.0") after lines 430 and 431.

Reported by Coverity CID 89807.

src/channel.c

@@ -522,8 +522,7 @@ channel_forward_listen(LIBSSH2_SESSION * session, const char *host,
                 }
                 else {
                     listener->session = session;
-                    memcpy(listener->host, host ? host : "0.0.0.0",
+                    memcpy(listener->host, host, session->fwdLstn_host_len);
-                           session->fwdLstn_host_len);
                     listener->host[session->fwdLstn_host_len] = 0;
                     if (data_len >= 5 && !port) {
                         listener->port = _libssh2_ntohu32(data + 1);