artik_examples: check argument stable
artik_examples: check argument stable

If the variable is negative, memory allocation for random bytes is not
possible.

Change-Id: I06021d59390089371f66a4a5b4320cd0c6c42513
Signed-off-by: Junhwan Park <7fee488b6f78fc50b291ffc7d10428788977e877@samsung.com>

JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT,JunhwanPark/TizenRT