Dynamic and linked offset fails with elliptical arcs

Steps to reproduce:

1. Draw two ellipses that either overlap or are concentric
2. Select both ellipses and apply path difference
3. Create a linked offset
4. Drag the linked offset handle away from the original object outline

What happened?

The linked offset does not follow the expected path.

Suspected cause

Offset does not operate correctly with paths defined using elliptical arcs. Offset appears to work correctly with the object created in step 2 above if it is first edited with a tool that implicitly converts it to Bezier curves, for example moving a node or applying path reverse.

Inkscape Version and Operating System:

• Inkscape 0.92.4 (5da689c313, 2019-01-14)
• Windows 10 Home 64-bit version 1809

Issue previously logged on Launchpad: https://bugs.launchpad.net/inkscape/+bug/1751166

Issue discussion on InkscapeForum.com: http://www.inkscapeforum.com/viewtopic.php?f=5&t=35024