Holding the confine movement modifier (Ctrl) while using the calligraphic tool shows a grey line on top left corner of screen

Summary:

There's a visual bug in the calligraphic tool when you hold the confine movement modifier key (default Ctrl) and move the mouse. A grey line appears from the left side of the window to the top left corner of the document.

Steps to reproduce:

• Switch to the calligraphic tool, and make sure it wasn't the last tool that was used
• Hold the confine movement modifier (Ctrl)
• Move the mouse

What happened?

A gray line gets drawn from the left side of the canvas to the top left corner of the document border.

If the top left corner of the document is below the middle of the screen, the line gets drawn to the middle of the left side of the canvas:

If the top left corner of the document is above the middle of the screen, the line gets drawn to the top left corner of the canvas:

What should have happened?

This line shouldn't exist. You can't produce the line if you've just drawn something with the calligraphic tool, because the line is an artifact from using the confine modifier with the calligraphic tool, which will try to draw a circle between the cursor and the nearest point on the last-drawn object (not sure what the name for this is).

Version Info:

- Inkscape Version: 1.1-alpha (1ffeedf4b1, 2021-01-28)
- Operating System: OpenSUSE Tumbleweed
- Operating System version: 20210129

I tested this in 1.0.1 (3bc2e813f5, 2020-09-07) and couldn't reproduce it.