[hotconv] fix warning for negative TypoLineGap.

[NSGod]

Description

This is a fix for #1653.

Checklist:

• I have followed the Contribution Guidelines
• I have added test code and data to prove that my code functions correctly
• I have verified that new and existing tests pass locally with my changes
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation

I ran tests locally and they all passed except the infinite loop one which always crashes for me.

It seems like it might be useful to have a new test that checks for that warning but I don't yet know enough about the testing framework to be able to write one myself.

[kaydeearts]

Thank you!