Crash undoing 3d box creation after tool switch

First reported in #2658

Steps to reproduce:

1. Open inkscape (no dialogs open)
2. draw a 3d box
3. switch to non-3d box tool (e.g. select or rect tool)
4. undo

What happened?

• crash, Backtrace: inkscape_backtrace-undo-3d-box.txt

What should have happened?

• noc crash

Version info

• Inkscape 1.2-dev (24f0b15c, 2021-07-16) Linux Mint 20
• Inkscape 1.1 (f559db2b, 2021-07-04) Linux Mint 20
• Inkscape 1.1 (c4e8f9ed, 2021-05-24) appimage Linux Mint 20,
• bisection points to 6f7f92c3