Inkscape does not show main window on request to open unsupported file type

Summary:

When requested to open an unsupported file type, Inkscape does not show its main window. However in a terminal window, repeated use of ps shows it is creating multiple processes, presumably indefinitely.

Steps to reproduce:

1. Use google dwebp program to convert webp file to yuv format: dwebp p33.webp -yuv -o p33.yuv (or just create an empty file touch p33.yuv or touch p33.svg). p33.webp is a file exported by GIMP from a PDF source file.
2. In desktop file manager window, select Inkscape to open p33.yuv

What happened?

• Inkscape main window does not appear.
• The same thing happened previously when I tried to open an unsupported file type that had been exported by GIMP.

What should have happened?

• Inkscape should have put up some indication that it couldn't open the file.
• GIMP and some others pop up a message box which you must close by clicking 'OK' button and then close the app.

Version Info:

• Inkscape Version: 1.0.1 (0767f8302a, 2020-10-17)
• Operating System: Linux
• Operating System version: Linux milton-MSI-Carbon 5.4.0-58-generic #64 (moved)-Ubuntu SMP Wed Dec 9 08:16:25 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux