[Dashboard] Added a proper message when Ray jobs submission is used a…

[orcahmlee]

Why are these changes needed?

I recently used the ray job submit CLI and got this confused error message

TypeError: 'NoneType' object is not callable

As the #41604 mentioned, it need a proper error message instead of raising NoneType error.

Related issue number

Related to #41604

Checks

• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[dayshah]

lgtm @rynewang to merge