Clone Original LPE crash if attribute has any whitespace (e.g. `d ` or `d, stroke`)

Summary:

Tried to follow the Clone Original video (https://www.youtube.com/watch?v=JAJAxKNY8lA). Inkscape crashes on two machines both running Mint 19 64 MATE.

Steps to reproduce:

• Created ellipse with fill and stroke
• Created rectangle with stroke
• Converted both to path
• Copied rectangular path
• Selected ellipse
• Assigned Clone Original effect
• Assigned d to attribute to link and pressed Set
• Clicked paste button in effect panel
• Instead Assigned d to attribute to link and pressed Set

What happened?

Crash (abort due to whitespace)

ERROR:../src/xml/simple-node.cpp:330:virtual void Inkscape::XML::SimpleNode::setAttributeImpl(const gchar*, const gchar*): assertion failed: (std::none_of(name, name + strlen(name), [](char c) { return g_ascii_isspace(c); }))

Obligatory Backtrace (not too relevant): inkscape-backtrace-assert-whitespace.txt

What should have happened?

Shape of ellipse should follow shape of rectangle.

Note the UI in the video is quite different from release.

Version Info:

- Inkscape Version: 1.0 (4035a4fb49, 2020-05-01)
- Operating System: Linux Mint 19 MATE 64