Fix error with a single byte being removed after the _ spacing character when rendering number formats

[MarkBaker]

This is:

- [X] a bugfix
- [ ] a new feature

Checklist:

• Changes are covered by unit tests
• Code style is respected
• Commit message explains why the change is made (see /~https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change
• Documentation is updated as necessary

Why this change is needed?

Fix error with a single byte being removed after the _ spacing character when rendering number formats

This is the fix for Issue #1924