Crashes when adding a path filter (Fillet)

Steps to reproduce:

• open new document
• add rectangle and convert it to path
• open path filters panel and add new filter
• select fillet
• crash

What happened?

Inkscape crashes with the following error:

Emergency save activated!

(inkscape:9738): GLib-CRITICAL **: 10:08:04.194: g_path_get_dirname: assertion 'file_name != NULL' failed

Emergency save document locations:
  /home/wout/Downloads/drawing.svg.2019_04_01_10_08_04.0.svg
Emergency save completed. Inkscape will close now.
If you can reproduce this crash, please file a bug at www.inkscape.org
with a detailed description of the steps leading to the crash, so we can fix it.
Segmentation fault (core dumped)

This bug was introduced in the past two weeks.

Inkscape Version and Operating System:

• Inkscape Version: Inkscape 1.0alpha (1:0.92.0+devel+201903312037+3967330)
• Operating System: Pop!_OS (Based on Ubuntu)
• Operating System version: 18.10