Gtk-WARNING **: 19:38:32.437: Theme parsing error:

[Robert Pearson]

When I report a bug in Ubuntu I get the following errors.

(apport-gtk:16883): Gtk-WARNING **: 18:54:44.036: Theme parsing error: gtk-widgets.css:3135:13: 'max-width' is not a valid property name

(apport-gtk:16883): Gtk-WARNING **: 18:54:44.037: Theme parsing error: gtk-widgets.css:3136:14: 'max-height' is not a valid property name

I saw a response that said to examine the style sheets and remove the 'max-width' and 'max-height'
properties. But I check with the CSS3 web-site and they are both valid property names.
See https://www.w3schools.com/cssref/pr_dim_max-height.asp
and https://www.w3schools.com/cssref/pr_dim_max-width.asp.

Should the warning ge Gtk-WARNING **: Gtk does not yet support the 'max-width' and 'max-height' properties? I do know that many of the CSS3 properties (like the 'rotation' property) are not yet supported.

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: apport-gtk 2.20.10-0ubuntu13.2
ProcVersionSignature: Ubuntu 4.18.0-16.17-generic 4.18.20
Uname: Linux 4.18.0-16-generic x86_64
ApportLog:

ApportVersion: 2.20.10-0ubuntu13.2
Architecture: amd64
CurrentDesktop: MATE
Date: Mon Mar 25 19:38:32 2019
InstallationDate: Installed on 2018-12-16 (99 days ago)
InstallationMedia: Ubuntu-MATE 18.10 "Cosmic Cuttlefish" - Release amd64 (20181017.2)
PackageArchitecture: all
SourcePackage: apport
UpgradeStatus: No upgrade log present (probably fresh install)