EMF+: mapping can rotate the width vector, so use resulting length.

Otherwise (i.e. with non-vertical lines) the width will be incorrect,
and can result in lines disappearing as the resulting X component
can be tiny/approaching zero.

Change-Id: Icf3b7c10c627594600b517b8ff445f8df87c56f8
(cherry picked from commit 83f2b3c590120a60b5e94fb1a15054ebe0745dbb)
Reviewed-on: https://gerrit.libreoffice.org/7249
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>