Fix orderBars to not die if first or last element in series is null

I need to submit that upstream as well.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fine tuning the hack to show better energy used values

With a few more data series it seems that I was correcting too aggressively.
This value seems to work most of the time in the samples that I have. We are
now always +/- 0.1kWh.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>