Additional reproduction test

I created a completely new Workbench project (separate addon) and world to rule out issues with my original project.

• Workbench version: 1.8.0.13

• New terrain: 128 × 128

• Terrain material: official Dirt_01.emat

• Painting the material works correctly.

• Clicking Terrain Tool → Manage → Rebuild terrain materials causes an immediate Workbench crash.

The issue is reproducible in a clean project without any custom terrain materials.

This is a separate crash from the previously reported issue when painting terrain materials with an enabled Plant Mat.

Try disabling the plant mat as a workaround