fix: handle empty show line results

[w3lld1]

Summary

Fixes #344 by making gto show <artifact>#<missing-stage> --version return an empty successful output instead of raising list index out of range when the underlying show result is empty.

Changes

• Guard show line-format output before indexing into an empty table result.
• Preserve the existing Cannot apply --<arg> validation for non-empty results that do not support the requested line flag.
• Add a regression test for an empty show --version result.

Verification

• pytest tests/test_cli.py::test_show_line_flag_empty_result tests/test_cli.py::test_commands tests/test_cli.py::test_show_ref_flag_not_applicable -q
• pytest -q
  • 189 passed, 1 warning
• python -m py_compile gto/*.py
• git diff --check

[Copilot]

Pull request overview

This PR fixes an IndexError in the gto show CLI when using a line-format flag (e.g. --version) and the underlying table result is empty (such as when querying a missing stage). Instead of crashing, the command now succeeds with empty output, matching the expectation described in issue #344.

Changes:

• Add an empty-result guard before indexing into the table rows when --name/--version/--stage/--ref line output is requested.
• Preserve Cannot apply --<arg> validation for non-empty results where the requested line flag doesn’t exist as a column.
• Add a regression test ensuring show ... --version returns success with empty stdout when the show result is empty.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
gto/cli.py	Prevents list index out of range by returning early for empty table row sets in line-format output mode.
tests/test_cli.py	Adds a regression test covering empty show --version output behavior.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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