Unhelpful error message when ArrayMesh has a shadow_mesh with a different number of surfaces

[BenLubar]

Tested versions

Initially found in 4.2.2 (Steam buildid 14084462).
Reproducible in 4.0-stable (after removing type hints on loops).
Reproducible in 4.1-stable (after removing type hints on loops).
Reproducible in 4.3-beta3.

System information

Godot v4.2.2.stable - Debian GNU/Linux trixie/sid trixie - Wayland - Vulkan (Forward+) - integrated Intel(R) Graphics (RPL-P) () - 13th Gen Intel(R) Core(TM) i7-1360P (16 Threads)

Issue description

The repro project spams the following errors in the output window:

ERROR: Index p_surface_index = 1 is out of bounds (mesh->surface_count = 1).
   at: mesh_get_surface (./servers/rendering/renderer_rd/storage_rd/mesh_storage.h:382)
ERROR: Index p_surface_index = 2 is out of bounds (mesh->surface_count = 1).
   at: mesh_get_surface (./servers/rendering/renderer_rd/storage_rd/mesh_storage.h:382)
ERROR: Index p_surface_index = 1 is out of bounds (mesh->surface_count = 1).
   at: mesh_get_surface (./servers/rendering/renderer_rd/storage_rd/mesh_storage.h:382)
ERROR: Index p_surface_index = 2 is out of bounds (mesh->surface_count = 1).
   at: mesh_get_surface (./servers/rendering/renderer_rd/storage_rd/mesh_storage.h:382)

There does not appear to be anything wrong visually, but obviously there is something wrong if it's spamming error messages.

Steps to reproduce

1. Open project
2. Observe output window

If the code in res://code/terrain/terrain_mesh.gd is removed, the error still occurs, but only once.

Minimal reproduction project (MRP)

voxel.zip