Disable Line Lists when there is no data

[pllim]

Description

This pull request is to fix #1669

Close #1690

Change log entry

• Is a change log needed? If yes, is it added to CHANGES.rst? If you want to avoid merge conflicts,
  list the proposed change log here for review and add to CHANGES.rst before merge. If no, maintainer
  should add a no-changelog-entry-needed label.

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• Are two approvals required? Branch protection rule does not check for the second approval. If a second approval is not necessary, please apply the trivial label.
• Do the proposed changes actually accomplish desired goals? Also manually run the affected example notebooks, if necessary.
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• Are tests added/updated as required? If so, do they follow the STScI Style Guides?
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• Did the CI pass? If not, are the failures related?
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• After merge, any internal documentations need updating (e.g., JIRA, Innerspace)?

[codecov]

Codecov Report

Base: 87.16% // Head: 87.16% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (38ca560) compared to base (970a915).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1691   +/-   ##
=======================================
  Coverage   87.16%   87.16%           
=======================================
  Files          95       95           
  Lines        9907     9913    +6     
=======================================
+ Hits         8635     8641    +6     
  Misses       1272     1272           

Impacted Files	Coverage Δ
...z/configs/default/plugins/line_lists/line_lists.py	74.67% <100.00%> (+0.33%)	⬆️

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[kecnry]

I think this is fine for now to "fix" the original bug, and then we can pick up #1690 in the future (likely as part of a refactor of the plugin, since I think even fixing the few things I found might uncover more problems).

[duytnguyendtn]

I think this is good enough for now, but for the refactor, I'd advocate for disabling the actual panel itself, rather than overriding the contents with a message: https://vuetifyjs.com/en/components/expansion-panels/#disabled

[pllim]

Thanks for the reviews!