Fix outline crash on empty heading with trailing space

[hiroakit]

Bugfix Overview

Outline generation could crash when an Org heading line is empty but contains a trailing space (e.g. ** ), causing the Outline view to show only partial results or “No symbols found in document”. The outline should remain functional and include subsequent headings even when empty headings exist.

Problem

• Observed behavior:
  • Documents containing an empty heading with a trailing space (e.g. ** ) can break symbol generation.
  • VS Code logs show name must not be falsy, and headings after the problematic line are missing from the Outline.
• Expected behavior:
  • Outline generation should not crash on empty headings; it should continue and show subsequent headings.

Reproduction Steps

1. Open an .org document containing a heading like ** (asterisks + space only).
2. Open the Outline view.
3. Observe missing headings after that line and/or “No symbols found in document”, with name must not be falsy in the console.

Root Cause

• utils.getHeaderTitle() could return an empty string for headings like ** .
• OrgFoldingAndOutlineDocumentState passes that title to SymbolInformation, and VS Code rejects falsy symbol names, throwing name must not be falsy and interrupting symbol computation.
• Why it was missed:
  • Existing tests did not exercise the Outline symbol provider path with empty headings.

Fix

• Fix approach:
  • Ensure getHeaderTitle() never returns an empty string by falling back to a placeholder ((empty heading)) when the extracted title is blank after trimming.
• Alternatives considered:
  • Skipping empty headings (would hide structure from Outline).
  • Handling it only in the outline provider (would duplicate title-normalization logic).

Verification

• Automated test added or updated
• Existing tests pass
• Test notes:
  • npm test
  • Added test/outline.test.ts to validate that vscode.executeDocumentSymbolProvider does not break on ** and that subsequent headings are still present.

Impact / Risk

• Affected users:
  • Anyone editing Org documents that contain empty headings with trailing spaces.
• Backward compatibility:
  • Low risk. Only affects the displayed name for empty headings in Outline.
• Potential side effects:
  • Empty headings will appear as (empty heading) in Outline instead of being blank (which previously crashed).

Related Issues / PRs

• Issue:
  • Outline view breaks if heading is empty with a trailing space vscode-org-mode/vscode-org-mode#218