Option::unwrap() failed in rend3::managers:material::apply_buffer_cpu()

[kpreid]

I haven't got a self-contained repro yet, but it involves loading an empty glTF scene with unused materials.

Backtrace:

   3: core::option::Option<T>::unwrap
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/option.rs:931:21
   4: rend3::managers::material::apply_buffer_cpu::{{closure}}
             at /Users/kpreid/.cargo/git/checkouts/rend3-e03f89403de3386a/a68c76a/rend3/src/managers/material.rs:319:48
   5: rend3::util::freelist::buffer::FreelistDerivedBuffer::apply::{{closure}}
             at /Users/kpreid/.cargo/git/checkouts/rend3-e03f89403de3386a/a68c76a/rend3/src/util/freelist/buffer.rs:94:24
   6: core::ops::function::impls::<impl core::ops::function::FnOnce<A> for &mut F>::call_once
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/ops/function.rs:305:13
   7: core::option::Option<T>::map
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/option.rs:1072:29
   8: <core::iter::adapters::map::Map<I,F> as core::iter::traits::iterator::Iterator>::next
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/iter/adapters/map.rs:103:26
   9: <core::iter::adapters::enumerate::Enumerate<I> as core::iter::traits::iterator::Iterator>::next
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/iter/adapters/enumerate.rs:47:17
  10: rend3::util::scatter_copy::ScatterCopy::execute_copy
             at /Users/kpreid/.cargo/git/checkouts/rend3-e03f89403de3386a/a68c76a/rend3/src/util/scatter_copy.rs:108:28
  11: rend3::util::freelist::buffer::FreelistDerivedBuffer::apply
             at /Users/kpreid/.cargo/git/checkouts/rend3-e03f89403de3386a/a68c76a/rend3/src/util/freelist/buffer.rs:101:9
  12: rend3::managers::material::apply_buffer_cpu
             at /Users/kpreid/.cargo/git/checkouts/rend3-e03f89403de3386a/a68c76a/rend3/src/managers/material.rs:318:5
  13: rend3::managers::material::MaterialManager::evaluate
             at /Users/kpreid/.cargo/git/checkouts/rend3-e03f89403de3386a/a68c76a/rend3/src/managers/material.rs:230:21
  14: rend3::renderer::eval::evaluate_instructions
             at /Users/kpreid/.cargo/git/checkouts/rend3-e03f89403de3386a/a68c76a/rend3/src/renderer/eval.rs:186:5
  15: rend3::renderer::Renderer::evaluate_instructions
             at /Users/kpreid/.cargo/git/checkouts/rend3-e03f89403de3386a/a68c76a/rend3/src/renderer/mod.rs:482:9
  16: gltf_render::GltfRend3Renderer::render_to_rend3
             at ./tests/gltf-render.rs:167:31

Code:

rend3/rend3/src/managers/material.rs

Line 319 in a68c76a

let material = &data_vec[idx].as_ref().unwrap().inner;

rend3 version: a68c76a