Crash with paint server dialog when there is an svg file in /paint

Steps to reproduce:

• save an svg file to your /paint folder in your user configuration directory (I used one with a pattern, or with nothing in the defs)
• open Inkscape
• open Object > Paint servers

What happened?

Immediate crash. Traceback

What should have happened?

No crash. Any pattern, hatch, etc. in that file should be included in:

• the corresponding dropdown in the Fill+Stroke dialog
• the Paint servers dialog

Inkscape Version and Operating System:

• Inkscape Version: 1.0beta2 (1e49a9bc2a, 2020-01-13)
• Operating System: Linux Mint 19.3