Presenterm will panic/crash if you hide all lines in a code block

[DrunkenToast]

Reproduce:

/// echo "hi"

will cause this:

thread 'main' panicked at src/processing/padding.rs:9:33:
argument of integer logarithm must be positive
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Expected behaviour: No/empty codeblock

[mfontanini]

Thanks!