app/test: fix crash after null check
app/test: fix crash after null check

In the kvargs test cases, we were checking for errors by checking if the
returned pointer value was NULL. In the error handling, we then tried to
free back the NULL pointer, which would cause a crash.

Signed-off-by: Bruce Richardson <66b9e8e8fbd5e9f41f91b0af050876182ce9d0e4@intel.com>

phermansson/dpdk,phermansson/dpdk,phermansson/dpdk,phermansson/dpdk