[GTK3]Cannot read SVG files from Adwaita theme?

[Fabrice DELENTE <fdelente mail cpod fr>]

Hello.

I have installed GTK3 on a Linux Slackware 13.37 distribution.

When I start a GTK3 app (for exemple, mount-gtk), I get these errors:

(mount-gtk:16839): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:620:27: Whitespace between 'url' and '(' is deprecated

(mount-gtk:16839): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:620:59: Couldn't recognise the image file format for file '/home/fab/.themes/Adwaita/gtk-3.0/assets/checkbox-unchecked.svg'

I have the latest Pango/ATK/Glib and GTK3 libs installed; what must I
do to get themes working in GTK3?

Thanks.

-- 
F. Delente