I recently rooted my phone, Samsung Galaxy S4 SGH-M919, and I edited the build.prop folder to get soft keys on my device. After I restarted my phone, the wallpaper changed to all black and about every 5 seconds I would get a message saying "Unfortunately, System UI has Stopped" so then I Un-rooted my phone through SuperSU and i still ended up getting the same problem. So then I decided to Factory Reset my phone, and afterwards the problem still didnt go away, I still got the same annoying message. I don't know what to do, please help ASAP, Thanks.