Panic in "accesskit_consumer" when running "state" example.

## Bevy version

12a11e2fd

## \[Optional\] Relevant system information

```
$ uname -a
Darwin fomo.local 23.1.0 Darwin Kernel Version 23.1.0: Mon Oct 9 21:28:45 PDT 2023; root:xnu-10002.41.9~6/RELEASE_ARM64_T6020 arm64

$ rustup show
Default host: aarch64-apple-darwin
rustup home: /Users/mburr/.rustup

installed toolchains
--------------------

stable-aarch64-apple-darwin (default)
nightly-aarch64-apple-darwin
1.65.0-aarch64-apple-darwin

installed targets for active toolchain
--------------------------------------

aarch64-apple-darwin
riscv32imc-unknown-none-elf

active toolchain
----------------

stable-aarch64-apple-darwin (default)
rustc 1.74.1 (a28077b28 2023-12-04)
```

## What you did

Attempted to run `cargo run --example state`

## What went wrong

```
thread 'main' panicked at /Users/mburr/.cargo/registry/src/index.crates.io-6f17d22bba15001f/accesskit_consumer-0.16.1/src/tree.rs:139:9:
assertion `left == right` failed
left: 1
right: 0
stack backtrace:
...
```

## Additional information

I do see a window flash briefly.

Start by reproducing the failure with `cargo run --example state` on the reported Bevy revision, then inspect the `state` example and the `accesskit_consumer-0.16.1/src/tree.rs` assertion shown in the backtrace. Done means the example launches without the panic and the briefly flashing window is replaced by a working example window.

Written by the indexing model from the issue text.