Network stats: Hide if there's no traffic (1/2)

https://github.com/scotthartbti/android_frameworks_base/commit/84779f4fa4a05437566fdabd0810c6e64d8ecfcf

PS2: fix checkbox derp
PS3: AOKP->System
PS4: Fix build

Change-Id: I2ca349fddb444dc828d843e151af4c458c1004e5