Fix crashes caused by tree support.

[ThomasRahm]

Description

Fix a hand full of crashes caused by tree support. Should fix at least: https://github.com/Ultimaker/Cura/issues/17688 https://github.com/Ultimaker/Cura/issues/17591 https://github.com/Ultimaker/Cura/issues/17549 https://github.com/Ultimaker/Cura/issues/17351 https://github.com/Ultimaker/Cura/issues/17670 https://github.com/Ultimaker/Cura/issues/17529 https://github.com/Ultimaker/Cura/issues/17479 https://github.com/Ultimaker/Cura/issues/17331 https://github.com/Ultimaker/Cura/issues/17655 https://github.com/Ultimaker/Cura/issues/17578 https://github.com/Ultimaker/Cura/issues/17597

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)

Test Configuration:

• Operating System: Windows 10

Checklist:

• [x] My code follows the style guidelines of this project as described in UltiMaker Meta
• [x] I have read the Contribution guide
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have uploaded any files required to test this change

[rburema]

Thanks once again Thomas!

(Devs: See internal ticket CURA-11519.)

[MariMakes]

For everyone checking in there is good news 🎉

This fix is included in the 5.7 Alpha, which has been released to analyze the incoming slicing crashes. If this crash is blocking you in any way you can download the nightly build to continue printing (and to help us analyze the slicing crashes)

You can find the downloads here https://github.com/Ultimaker/Cura/discussions/18080