Removed path effects remain in saved files

Steps to reproduce:

1. Draw a curve.
2. Add a path effect.
3. Delete the applied effect.
4. Save.

What happened?

SVG file contains the removed effect in <defs>

What should have happened?

<inkscape:path-effect> should not be included

Inkscape Version and Operating System:

Windows 10 x64

Inkscape 1.0 Beta 1