Transpose down -1 stops

[angeloskalaitzakis]

When you transpose up +1 it circles through the chords it goes up to 12 semitones and starts over again.
However when you transpose down -1 it stops after 13 semitones.

i have also modified your code and added some markdowns. etc
[tab]
e|---------------------------------------------------------------------------|
B|---------------------------------------------------------------------------|
G|---------------------------------------------------------------------------|
D|---------------------------------------------------------------------------|
A|---------------------------------------------------------------------------|
E|---------------------------------------------------------------------------|
[/tab]

[chorus]
This is a chorus
[/chorus]

[comment]
this is a comment
[/comment]

let me know if you want the code.

[nadunindunil]

Hi @angeloskalaitzakis ,
Thank you very much for the issue.

I was able to recreate the issue.
Would you mind submitting a PR ?

Attached is an error log herewith.

[angeloskalaitzakis]

I have fixed this ill try upload.

[nadunindunil]

This was fixed at #13