Compatability with Grafana >= 6.5.0

[c-thiel]

When using the grouped-bar-chart with Grafana >= 6.5.0 I get the following Error:

An unexpected error happened
Details
TypeError: Cannot read property 'Dark' of undefined
  in t
  in div
  in t
  in div
  in r
  in c
  in div
  in div
...

Screenshot

Downgrading grafana to 6.4.X fixes the Issue for me.
I checked the grafana changelog, but don't believe that those breaking changes should affect this.

Can anyone confirm this issue?

[Amaradana]

please help in 6.5.1

[gipong]

it seems that this issue is related to #8. i have reverted the changes to previous version.

[truj]

Similar problem with Grafana 7.1.0
JS-Error:

angular.js:14800 TypeError: Cannot read property 'Dark' of undefined
    at getCurrentThemeName (ctrl.js:38)
    at getCurrentTheme (ctrl.js:39)
    at new groupedBarChart (ctrl.js:124)
    at onRender (ctrl.js:444)
    at s.eval (ctrl.js:467)
    at s.emit (index.js:202)
    at e.value (emitter.ts:29)
    at GroupedBarChartCtrl.value (panel_ctrl.ts:102)
    at panel_directive.ts:64
    at angular.js:20566