feMorphology: same as for feGaussianBlur, explicitly ignore non-positive radiuses
feMorphology: same as for feGaussianBlur, explicitly ignore non-positive radiuses

Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/763>

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