`clean-conversation-sidebar`: unable to add Labels to PRs (when no prior labels defined)

Description

When that feature is enabled, the sidebar is "clean" on existing PRs. Labels are not shown if not defined on the PR.

Issue

I am not able to add a (first) label to the PR once it is created without any label: the gear and the function to add them is not shown in the sidebar anymore.

Notes:

• if there is an existing label, the gear to add additional labels is shown and all works fine.
• No console errors are shown.

Workarounds

1. To quickly add "labels" I use Firefox's "Reload without Refined GitHub" extension's menu (which disables the extension): then the "Labels" section on the sidebar is shown and I can add the first label.
2. When I disable the clean-conversation-sidebar feature I see the "original" sidebar with the labels section.

Wish/Fix

I would like to be able to keep the clean-conversation-sidebar feature enabled, and still add a first label to already created PRs.

How to replicate the issue + URL

1. create a PR on github: do NOT add labels
2. open the PR again, try to add a label

What I see is the following, where I can not add any label

Extension version

26.3.17

Browser(s) used

Firefox 148.0.2 (64-bit)

Token ⚠️

• I set a token in the options page. I understand that some features require a token to work.