net/virtio: fix crash on null dereference
net/virtio: fix crash on null dereference

The rxq/txq for the queue_release callback could be NULL, say when
rte_eth_dev_configure() fails that the queue is not setup at all.

Do a simple NULL check would fix the crash issue.

Fixes: 01ad44fd374f ("net/virtio: split Rx/Tx queue")

Reported-by: Olivier Matz <dfcc1510895413197abb4336e39bb0a3906cba71@6wind.com>
Signed-off-by: Yuanhan Liu <5dcef21195e64c9c08aa779bb62b25e9133eaa33@linux.intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk