Tainted and unvalidated integer 'idx' used as an index, which may
lead to buffer overflow.
This patch fixed it.
Fixes: 89e5eb118017 ("app/testeventdev: add string parsing helpers")
Cc: stable@dpdk.org
Signed-off-by: Min Hu (Connor) <humin29@huawei.com>
Acked-by: Pavan Nikhilesh <pbhagavatula@marvell.com>