/blockdata ~ ~ ~ {Items:[]} does not work at a certain distance away from the player
Solution 1:
When the oldBlockHandlingValue on the /setblock command is destroy, the block will drop itself and its contents (Unless gamerules prohibit it). However, if you use replace instead, the chest will drop neither itself nor its contents.
Also, using redstone with command blocks is an excellent way to start learning command blocks. You'll eventually want to learn about chain and repeating command blocks and functions, and certainly use functions for anything large scale, but using just normal command blocks for small things, learning and experimenting is fine.