remove check for readings unavailable

[huss]

Is your feature request related to a problem? Please describe.

Before the Redux Toolkit, src/client/app/components/RadarChartComponent.tsx checked for readings === undefined because the reading might still being fetched. This probably no longer needs to be done. See the TODO in that file.

Describe the solution you'd like

Remove and test that okay.

Describe alternatives you've considered

Don't remove code.

Additional context

None

[danielshid]

I will be working on this issue.