Clicking on container tab or away from container tab shifts all tabs positions to the right or left

# Setup

* Install Containers Theme 1.0.2
* Open a number of tabs greater than the number that fit in Firefox such that firefox makes them scrollable left to right
* Make one of those tabs a container tab in any position but the far right (newest tab)
* Select the far right (newest tab) which is not a container tab
* Select the container tab

# Expected results

The selected container tab should be come active and the scrolled positioning of the tabs should not change

# Actual results

The container tab gets scrolled to the far right, and the tabs to the right of it are scrolled off the right side of the page.

This also happens when selecting away from the container tab.

Here's a video of the bug happening

[](https://www.youtube.com/watch?v=ItNOhvf0-FQ)
(I'd intended in the beginning to show the version of Containers Theme (which is 1.0.2) not the version of the Firefox Multi-Account Containers add-on)

Reproduce the tab-scrolling behavior in Firefox using the setup and selection steps in the issue, including selecting away from the container tab. Inspect the extension's tab and container styling entry points to find what changes the tab positions; done means selecting either tab preserves the existing scroll position while keeping the selected tab active.

Written by the indexing model from the issue text.