frontend: Show message in case of uncompleted trial instead of the graph

[elenzio9]

In this PR, we implement the following:

• Show message in case of uncompleted trial instead of the graph.
  
• Add some text below the spinner in order to inform users why we're spinning about.
  

[tenzen-y]

HI, @elenzio9!
Thanks for this improvement!

Some CI jobs seem to fail, but the errors will be fixed once #2064 is merged with the master branch.

@kimwnasptd Could you help review this PR?

/assign @kimwnasptd

[elenzio9]

HI, @elenzio9! Thanks for this improvement!

Some CI jobs seem to fail, but the errors will be fixed once #2064 is merged with the master branch.

Your welcome! OK, thanks!

[tenzen-y]

@elenzio9 Can you rebase this since we have merged #2064 into the master branch?

[elenzio9]

@elenzio9 Can you rebase this since we have merged #2064 into the master branch?

I just force pushed!

[orfeas-k]

The code looks good. I also tested the PR's image and everything works as expected. Thank you @elenzio9 for this improvement!
cc @kimwnasptd
/lgtm

[kimwnasptd]

Thank you for taking a look @orfeas-k!

/lgtm
/approve

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: elenzio9, kimwnasptd

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