don't crash on return to sleepmeter statistics page after exit using home/circle/square
Sleepmeter crashes under the following circumstances:
- show the statistics page
- exit sleepmeter using home/circle/square
- do lots of other things with the device that use lots of device resources
- return to sleepmeter
It crashes with a back trace that contains a NPE during a hindrance comparison but the real problem is that the state is being restored before the hindrance resolution has been setup.