Fix panic when using tags

[danpoltawski]

Before this patch it was bombing out with:

panic: runtime error: index out of range [1] with length 0

goroutine 1 [running]:
main.visit({0x14000016d80, 0x40}, {0x1026579a8?, 0x140001008f0?}, {0x14000016d80?, 0x40?})
	/Users/danp/git/octohug/octohug.go:161 +0xd8c
path/filepath.walk({0x14000016d80, 0x40}, {0x1026579a8, 0x140001008f0}, 0x102656808)
	/opt/homebrew/Cellar/go/1.22.1/libexec/src/path/filepath/path.go:478 +0xc8
path/filepath.walk({0x10260c87b, 0xd}, {0x1026579a8, 0x14000100820}, 0x102656808)
	/opt/homebrew/Cellar/go/1.22.1/libexec/src/path/filepath/path.go:502 +0x1d0
path/filepath.Walk({0x10260c87b, 0xd}, 0x102656808)
	/opt/homebrew/Cellar/go/1.22.1/libexec/src/path/filepath/path.go:560 +0x6c
main.main()
	/Users/danp/git/octohug/octohug.go:237 +0xf4

On a posts which has the format:

categories:
- one
- two
tags:
- converted
sidebar: collapse
comments: true

And it seemed to match the sidebar line here.

I haven't fully understood how this was supposed to be working before/how my post format was wrong, but this fix allows it to run and seems to do the right thing

[codebrane]

thanks for the fix