pwr/Solaar — pull request #126 by slaveriq (2013-09-24 15:00:55+00:00)
Title: Fixing a crash when level is type None

level is returned as None in hidpp10.py when the performanceMX mouse is charging. Since the battery state is unknown when beeing recharged it
will now return "N/A".
Before it would crash becasue level was None and could not be inserted
using %d.