Morphology needs positive radii even after the transformation

Morphology needs positive radii even after the transformation

This is the same pattern as in gaussian_blur.rs; the paffine
transformation can leave us with negative radii, so take their
absolute value after the transformation.

This fixes assertion error (crashing) when nagative r takes place.

Forwarded: https://gitlab.gnome.org/GNOME/librsvg/issues/395
Applied-Upstream: https://gitlab.gnome.org/GNOME/librsvg/commit/4ef7f198fceb8fb4a544f4768174af5b11fc9bcc
Bug-Debian: https://bugs.debian.org/927886
Signed-off-by: Boyuan Yang <byang@debian.org>
Gbp-Pq: Name keep-positive-radii.patch