Attempt to fix minimum brightness setting

At the moment brillo -rc -S 1 -v 3 does not work for me giving an error that it cannot open the file ~/.cache/brillo/backlight.intel_backlight.mincap It seems this can be partially fixed by obtaining the previous value before opening the output file for writing. However I don't see the need to check the original value for this and the program does not seem to initialise this file if it does not exist and instead just crashes. For this reason I wonder if something more has gone wrong.