ProxLight Override - Proximity APP
So if you have problems with the proximity sensor and your device screen does not turn black, this can help you out !!
Also you can use the light sensor to turn the device screen off when your head is close if you have problems with the Proximity sensor (still beta, not all light sensors have same values).
This app uses the Device permission.
The app must have this permission to lock the screen when want to use light sensor instead of proximity sensor.(You can disable it easy from App menu)