<!--
NOTE: Please read the guidline to open a new issue at first.
https://github.com/piroor/treestyletab/blob/master/CONTRIBUTING.md
-->

## Short description

## Steps to reproduce

 1. Start Filrefox with clean profile.
 2. Install TST.
 3. 
 4. 

## Expected result


## Actual result


## Environment

 * Platform (OS): 
 * Version of Firefox: 
 * Version (or revision) of Tree Style Tab: