tools: rina-echo-async: fix out-of-bounds array access
tools: rina-echo-async: fix out-of-bounds array access

vmaffione/rlite,autrimpo/rlite,vmaffione/rlite,vmaffione/rlite,autrimpo/rlite,vmaffione/rlite,autrimpo/rlite,autrimpo/rlite