MeshDataBindings::SetSubMeshImpl -> UpdateSharedDataSubMeshVertexRange

GetVertexBufferRange(::GetSubMeshBuffer32(submesh, &data), submesh.indexCount, submesh.firstVertex, lastVertex);
first parameter is null, so we have a crash inside GetVertexBufferRange

Cannot reproduce it with old SetTriangles API.

Sidenote: inside MeshScripting::InternalSetIndexBufferData

Sometimes
Mesh::IndexContainer& buffer = m->GetWritableIndexBuffer();
if (meshBufferStartBytes + countBytes > buffer.size())
{
*outException = Scripting::CreateArgumentException("Accessing %zu bytes at offset %zu for mesh index buffer of size %zu bytes is not possible.", countBytes, meshBufferStartBytes, buffer.size());
return;
}

buffer.capacity() is correct, but buffer.size() is less than capacity for unknown reason.

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STEPS:
1) Open attached project
2) Open the scene file inside
3) Click on the sphere and make sure DebugTestChange's changeMaterial is enabled and list of materials is not empty
HexasphereMaterialData.UseNewMeshAPI = false -- has expected behavior
HexasphereMaterialData.UseNewMeshAPI = true -- some hexes will disappear, then hard crash of Unity Editor on access violation