gitlab#263 - Ignore errors when parsing CSS values
gitlab#263 - Ignore errors when parsing CSS values

Per the CSS spec, values which can't be parsed should be ignored.  We
were setting the whole node to be in error.

https://gitlab.gnome.org/GNOME/librsvg/issues/263

GNOME/librsvg,GNOME/librsvg,GNOME/librsvg,GNOME/librsvg