Failed sub-asset loads can get stuck in `LoadState::Loading`

[greeble-dev]

Bevy version

0.18

What you did

// Load a labeled sub-asset that doesn't exist.
let handle = asset_server.load::<AssetType>("asset#non_existent_subasset");

// Or load a labeled sub-asset that does exist, but is not of type `WrongAssetType`.
let handle = asset_server.load::<WrongAssetType>("asset#subasset");

What went wrong

I expected AssetServer::get_load_state(handle) to eventually return LoadState::Failed with an appropriate error. But instead it gets stuck in LoadState::Loading.

[greeble-dev]

Tagging with S-Waiting-on-Author as I expect to file a PR with a partial fix.