Patch bugs in full-text links logic

[jazairi]

Why these changes are being introduced:

There are two uncaught edge cases in the full-text link logic:

1. Full-text options are removed when libkey links exist.
2. I a PNX record as an empty links object (rather than omitting it altogether), then full-text
   options will not display.

Relevant ticket(s):

• USE-663

How this addresses that need:

This addresses the edge cases noted above.

Side effects of this change:

This change was prompted by full-text links not
appearing in staging, despite working properly in
local development environments. It's unclear
whether this change is what's required to fix
staging.

Developer

Accessibility

• ANDI or WAVE has been run in accordance to our guide.
• This PR contains no changes to the view layer.
• New issues flagged by ANDI or WAVE have been resolved.
• New issues flagged by ANDI or WAVE have been ticketed (link in the Pull Request details above).
• No new accessibility issues have been flagged.

New ENV

• All new ENV is documented in README.
• All new ENV has been added to Heroku Pipeline, Staging and Prod.
• ENV has not changed.

Approval beyond code review

• UXWS/stakeholder approval has been confirmed.
• UXWS/stakeholder review will be completed retroactively.
• UXWS/stakeholder review is not needed.

Additional context needed to review

E.g., if the PR includes updated dependencies and/or data
migration, or how to confirm the feature is working.

Code Reviewer

Code

• I have confirmed that the code works as intended.
• Any CodeClimate issues have been fixed or confirmed as
  added technical debt.

Documentation

• The commit message is clear and follows our guidelines
  (not just this pull request message).
• The documentation has been updated or is unnecessary.
• New dependencies are appropriate or there were no changes.

Testing

• There are appropriate tests covering any new functionality.
• No additional test coverage is required.

[qltysh]

❌ 4 blocking issues (4 total)

Tool	Category	Rule	Count
rubocop	Lint	Assignment Branch Condition size for links is too high. [<4, 48, 16> 50.75/17]	1	❌
rubocop	Lint	Cyclomatic complexity for links is too high. [17/7]	1	❌
rubocop	Lint	Method has too many lines. [27/10]	1	❌
rubocop	Lint	Perceived complexity for links is too high. [18/8]	1	❌

[coveralls]

Coverage Report for CI Build 33194305177

Coverage remained the same at 98.3%

Details

• Coverage remained the same as the base build.
• Patch coverage: 3 of 3 lines across 1 file are fully covered (100%).
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	1706
Covered Lines:	1677
Line Coverage:	98.3%
Coverage Strength:	81.61 hits per line

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💛 - Coveralls