Fix issue in parser when calculating line numbers with non-empty section header

[e859127]

[SuperMeepEnby]

Hey @e859127 ! Can you by any chance show me a way to reproduce the bug so I can understand more clearly?

Your input
What you do?
What you expect?
What you get?

I see your PR has not been read yet and I started maintaining it on my side. This would help me.

Thanks a lot!