ui: Add error boundary in the React UI

[onprem]

• I added CHANGELOG entry for this change.
• Change is not relevant to the end user.

Changes

• Add a error boundary to the React UI. Now in case of an irrecoverable error, users would see a "Something went wrong" page instead of a blank screen.
• Fix the crash when there is no store connected to the Querier. The crash was because the API response for /api/v1/label/__name__/values was

{
  "status": "success",
  "data": null
}

Here, the UI expects data to be an array.
Fixed this by sending an empty array ([]) instead of null

Verification

Tested locally by emulating error conditions.

Screenshot

[bwplotka]

Awesome! One comment, then LGTM

[squat]

Looks great :)))

[squat]

If this is the only instance of the detailsBtn class, why split the font size out of the css? To keep the css class more generic?

[onprem]

The internal bootstrap classes were getting priority over the detailsBtn class, so I wasn't able to modify the font-size here. I had two options, either use !important on use inline CSS.

I think maybe there is a third solution too. I can increase the specificity of detailsBtn class, by declaring it as button.detailsBtn or something.

[onprem]

Using button.detailsBtn instead of just .detailsBtn worked 🎉

[squat]

yes let's avoid !important for sure. making it more specialized 👍

[squat]

looks great. See,s that we need to fix a linting error. This may require regeneration of the bindata.go