lws_get_peer_write_allowance: cope with no role callback for it
lws_get_peer_write_allowance: cope with no role callback for it

https://github.com/warmcat/libwebsockets/issues/1339
sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets,sartura/libwebsockets