Check that poll answer index is not negative, to avoid a Prelude.!! error

[smelc]

Changelog

- description: |
    Check that poll answer index is not negative. This replaces a Prelude.!! error by a regular `GovernanceCmdError` error
# uncomment types applicable to the change:
  type:
  # - feature        # introduces a new feature
  # - breaking       # the API has changed in a breaking way
  - compatible     # the API has changed but is non-breaking
  # - optimisation   # measurable performance improvements
  # - improvement    # QoL changes e.g. refactoring
  - bugfix         # fixes a defect
  # - test           # fixes/modifies tests
  # - maintenance    # not directly related to the code
  # - release        # related to a new release preparation
  # - documentation  # change in code docs, haddocks...

Context

Fixes IntersectMBO/cardano-node#5182

How to trust this PR

Execute before the PR, observe Prelude.!! error:

→ cabal run cardano-cli -- governance answer-poll --poll-file cardano-cli/test/cardano-cli-golden/files/input/governance/polls/basic.json --answer -1

cardano-cli: Prelude.!!: negative index

Execute on this PR, witness it fails with a regular error:

→ cabal run cardano-cli -- governance answer-poll --poll-file cardano-cli/test/cardano-cli-golden/files/input/governance/polls/basic.json --answer -1
Command failed: governance answer-poll  Error: Poll answer out of bounds. Choices are between 0 and 1

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• The change log section in the PR description has been filled in
• NA New tests are added if needed and existing tests are updated. These may include:
  • golden tests
  • property tests
  • round trip tests
  • integration tests
    See Running tests for more details
• NA The version bounds in .cabal files are updated
• CI passes. See note on CI. The following CI checks are required:
• Self-reviewed the diff

[smelc]

Minimalist one to finish my day 😸

[carlhammann]

LGTM ... and the rendering of the error that's thrown is still correct.