Fix regression introduced by refactoring `Segment`

As part of a refactoring effort (!113) [1], commit f05d2fcb renamed
`inkex.transforms.Segment` to `DirectedLineSegment` and also changed its
constructor signature so that its single-argument variant no longer
accepts a tuple of 2D vectors.

Instead, the single-argument constructor now only accepts another
`DirectedLineSegment` so it has essentially become a copy constructor.

However, not all call sites were updated, which causes an
`AttributeError` when attempting to call the new constructor with
a, previously valid, tuple of 2D vectors.

Fix the call site to use the two-argument variant, avoiding the error.

[1]: inkscape/extensions!113

CC: Sergei Izmailov <sergei.a.izmailov@gmail.com>