## Summary
- Fixed a debug build assertion failure in PostgreSQL error handling
when all error message fields are empty
- Added safety check before calling `StringBuilder.allocatedSlice()` to
handle zero-length messages
- Added regression test to prevent future occurrences
## The Problem
When PostgreSQL sends an error response with completely empty message
fields, the `ErrorResponse.toJS` function would:
1. Calculate `b.cap` but end up with `b.len = 0` (no actual content)
2. Call `b.allocatedSlice()[0..b.len]` unconditionally
3. Trigger an assertion in `StringBuilder.allocatedSlice()` that
requires `cap > 0`
This only affected debug builds since the assertion is compiled out in
release builds.
## The Fix
Check if `b.len > 0` before calling `allocatedSlice()`. If there's no
content, use an empty string instead.
## Test Plan
- [x] Added regression test that triggers the exact crash scenario
- [x] Verified test crashes without the fix (debug build)
- [x] Verified test passes with the fix
- [x] Confirmed release builds were not affected
🤖 Generated with [Claude Code](https://claude.ai/code)
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Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
