Crash on import with UDIM when UV vertex is placed across 2 UDIM tiles

Issue still not solved https://github.com/armory3d/armortools/issues/1163 but I cannot reopen it

here is another model that results in a crash when seperating by udim:

[SimpleCollectionOfficeChair.zip](https://github.com/user-attachments/files/18867273/SimpleCollectionOfficeChair.zip)


**ArmorPaint version:**
I tried 10alpha and 09 from gumroad

**OS / GPU model:**
Win 10
3080 Ti

**Issue description:**

When importing the obj mesh and selecting seperating by UDIM the program just crashes without error message.
Importing it with selecting seperate by object works.

**Steps to reproduce:**
1. Download the model
2. Open Armor Paint
3. Import mesh
4. Set to seperate by UDIM
5. Click import
6. Crash

Reproduce the crash in ArmorPaint using the attached SimpleCollectionOfficeChair.zip, following the six import steps with Separate by UDIM enabled. Compare that result with Separate by Object and trace the mesh-import path involved; done means the model imports with UDIM separation without crashing or silently failing.

Written by the indexing model from the issue text.