Fix battery widget with upower <= 0.99.7

[rrrapha]

The should fix the "Battery status unknown" issue reported in #2161
(I have not tested this on ubuntu)

[ronso0]

Perfect, thanks for the fix!
Now the widget shows the same information as the OS indicator

works in Ubuntu Studio 18.04 w/ upower 0.99.7-2ubuntu0.18.04.1

[daschuer]

Sometimes the obvious fix is hidden ... thank you for discovering.

I can confirm that this also works with upower 0.99.4 on Ubuntu Xenial 16.4

This issue exists also in the maintained 2.2 branch. Please rebase your changes to that
force push and change here the target branch.
Or just issue a new PR.
Thanks.

[uklotzde]

Merge? I already added an entry to the changelog in #2225.

[uklotzde]

The Windows build failure is unrelated.

[rrrapha]

Merge? I already added an entry to the changelog in #2225.

I think the battery widget is still broken in 2.2 without the following change:
https://github.com/mixxxdj/mixxx/pull/2146/files
Maybe this should be backported to 2.2?

[uklotzde]

Yes, of course. Just cherry pick that commit.

[ronso0]

Perfect, thanks for the fix!
Now the widget shows the same information as the OS indicator

works in Ubuntu Studio 18.04 w/ upower 0.99.7-2ubuntu0.18.04.1

Whoops, I just noticed this is targetd at 2.2. I only tested with master..

[uklotzde]

LGTM. Thank you! Those nasty kind of bugs are sometimes hard to discover.