Description of problem:

when using breeze-gtk as theme in XFCE4 on RHEL 8.8, I get an avalanche of warnings regarding parsing errors Missing closing bracket for :not()

(xfce4-panel:740186): Gtk-WARNING **: 21:26:48.660: Theme parsing error: gtk.css:978:50: Missing closing bracket for :not()

(xfce4-panel:740186): Gtk-WARNING **: 21:26:48.660: Theme parsing error: gtk.css:983:52: Missing closing bracket for :not()

(xfce4-panel:740186): Gtk-WARNING **: 21:26:48.660: Theme parsing error: gtk.css:987:52: Missing closing bracket for :not()

(xfce4-panel:740186): Gtk-WARNING **: 21:26:48.660: Theme parsing error: gtk.css:992:52: Missing closing bracket for :not()

(xfce4-panel:740186): Gtk-WARNING **: 21:26:48.660: Theme parsing error: gtk.css:996:52: Missing closing bracket for :not()

(xfce4-panel:740186): Gtk-WARNING **: 21:26:48.660: Theme parsing error: gtk.css:999:52: Missing closing bracket for :not()

Version-Release number of selected component (if applicable):

5.24.7-1.el8

How reproducible:

Install XFCE4, breeze-gtk, and set the theme to Breeze-dark for exemple in the settings.

Steps to Reproduce:
1. install xfce4 desktop envirement in RHEL8
2. install breeze-gtk theme
3. set the theme in XFCE setting
4. start session

Actual results:

Avalanche of Gtk-WARNING ** Theme parsing error: gtk.css Missing closing bracket for :not() messages

Expected results:

No Warnings like the default theme.

Additional info: