fs/fscmd : Fix memfault of echo
fs/fscmd : Fix memfault of echo

If user type just 'echo' memfault happened because args[1] is null so fix it.

jsdosa/TizenRT,jeongchanKim/TizenRT,pillip8282/TizenRT,jsdosa/TizenRT,jeongarmy/TizenRT,jeongarmy/TizenRT,jeongarmy/TizenRT,jeongarmy/TizenRT,junmin-kim/TizenRT,jeongarmy/TizenRT,jeongchanKim/TizenRT,an4967/TizenRT,sunghan-chang/TizenRT,an4967/TizenRT,Samsung/TizenRT,jeongchanKim/TizenRT,an4967/TizenRT,sunghan-chang/TizenRT,junmin-kim/TizenRT,Samsung/TizenRT,pillip8282/TizenRT,jsdosa/TizenRT,jeongarmy/TizenRT,junmin-kim/TizenRT,Samsung/TizenRT,Samsung/TizenRT,pillip8282/TizenRT,jsdosa/TizenRT,jeongchanKim/TizenRT,junmin-kim/TizenRT,an4967/TizenRT,jeongarmy/TizenRT,sunghan-chang/TizenRT,sunghan-chang/TizenRT,jeongchanKim/TizenRT,an4967/TizenRT,jsdosa/TizenRT,pillip8282/TizenRT,sunghan-chang/TizenRT,jeongchanKim/TizenRT,Samsung/TizenRT,pillip8282/TizenRT,Samsung/TizenRT,sunghan-chang/TizenRT,junmin-kim/TizenRT,jsdosa/TizenRT,Samsung/TizenRT,junmin-kim/TizenRT,an4967/TizenRT,sunghan-chang/TizenRT,jsdosa/TizenRT,an4967/TizenRT,junmin-kim/TizenRT,pillip8282/TizenRT,jeongchanKim/TizenRT,pillip8282/TizenRT