Voxel Sandcastle Crashes in FIrefox

### What happened?

[This Voxel sandcastle](https://sandcastle.cesium.com/?src=Voxels.html) crashes instantly in Firefox (Cesium 1.130, macOS Sequoia 15.5, M4 Max, Firefox version 139.0.4 (aarch64)).

It does *not* crash in Chrome.

### Reproduction steps

1. Open Firefox
2. Load [this sandcastle](https://sandcastle.cesium.com/?src=Voxels.html)
3. Witness crash

### Sandcastle example

https://sandcastle.cesium.com/?src=Voxels.html

### Environment

Browser: Firefox
CesiumJS Version: 1.130
Operating System: macOS Sequoia 15.5

Start by reproducing the crash with the linked Voxel sandcastle in Firefox 139.0.4 and compare its behavior with Chrome using Cesium 1.130 on the reported macOS environment. Trace the Voxel example from the Sandcastle link to identify the failing path; done means the example no longer crashes in Firefox and still works in Chrome.

Written by the indexing model from the issue text.