Fix whisper messages not getting different background in t2k4e.css

[tinwe]

Fix whisper messages not getting different background in t2k4e.css

Summary

Fixes the bug where whisper and hidden messages does not get a different background

(Your summary.)

Checklist

PR Type

• This PR is a code change that implements a feature request.
• [X ] This PR fixes an issue.
• This PR adds a new feature that is not an open feature request.
• This PR is not a code change (e.g. documentation, README, ...)

Other

• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• If code changes were made then they have been tested.
• I have updated the documentation to reflect the changes (wiki).

[tinwe]

Sorry, should have been background_texture.webp not paper_texture.webp

[tinwe]

Still works, and gives the vanilla grey background, but gives an unnecessary broken background image load