Adding Perspective LPE to purely horizontal or vertical path causes crash

Summary:

When adding a Perspective LPE to a path, Inkscape crashes for me. This might be related to #1415

Steps to reproduce:

• open Inkscape and load ekman.svg
• click on any arrow (I tested with top two)
• go to Path -> Effects -> add effect -> perspective

What happened?

Inkscape crashes with

gsl: lu.c:311: ERROR: matrix is singular
Default GSL error handler invoked.

What should have happened?

Inkscape shouldn't crash.

Attachments:

ekman.svg inkscape_crash

Version Info:

- Inkscape Version: Inkscape 1.0.1 (3bc2e813f5, 2020-09-07, custom), Pango version: 1.48.0
- Operating System: Arch Linux
- Operating System version: 5.10.9-arch1-1