[regression] Tabs in Settings of Thunderbird not visible

[Gre0]

I am on Ubuntu 18.04 Bionic right now and noticed a little theme missbehavior. (i think)

>> Open 'Thunderbird'...go into 'Settings'...go to 'Security' (for example)

There the Tabs below (Junk, Password, ...) are not visible.
There is just text with no background (see screenhot)

Sidenote: The same i noticed on Xubuntu with greybird-theme. But with other themes (numix, arc) they are visible.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: light-themes 16.10+18.04.20180122.1-0ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-10.11-generic 4.15.3
Uname: Linux 4.15.0-10-generic x86_64
ApportVersion: 2.20.8-0ubuntu10
Architecture: amd64
CasperVersion: 1.389
CurrentDesktop: ubuntu:GNOME
Date: Fri Mar 9 15:26:35 2018
LiveMediaBuild: Ubuntu 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180308)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-themes
UpgradeStatus: No upgrade log present (probably fresh install)

[Gre0 (gre0)]

The same window with Adwaita-theme is ok.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Daniel van Vugt (vanvugt)]

Yeah.

It's fine in 16.04 and broken in 18.04. Not quite sure when it broke.