Bug#921524: thunderbird ignores theme setting in .config/gtk-3.0/settings.ini

[sergio]

Package: thunderbird
Version: 1:60.5.0-3
Severity: normal


thunderbird ignores

gtk-application-prefer-dark-theme = true

from

.config/gtk-3.0/settings.ini

but respects 

$GTK_THEME=Adwaita:dark

All other apps works fine.