We need a useful error message when two materials have the save UUID

[eliotbo]

Bevy version

0.6,

What you did

Take the shader_material example and add second material to it with the same UUID, but different name.

What you expected to happen

I expected either a run time error message or a warning about having two identical UUID.

What actually happened

There was a runtime error with not much information:

thread 'Compute Task Pool (20)' panicked at 'called `Option::unwrap()` on a `None` value', /home/eliotbolduc/Documents/rust/bevy_fork/crates/bevy_asset/src/asset_server.rs:505:14

It refers to this line in asset_server.rs:

let channel = asset_lifecycle
       .downcast_ref::<AssetLifecycleChannel<T>>()
       .unwrap(); ```

[rparrett]

Related: #2610

[ByAlu]

@alice-i-cecile This is my first time contributing. I don't know rust language but I have some programming experience. May I work on this issue?

[alice-i-cecile]

@ByAlu absolutely! Just open a PR and then link this issue :)

[mockersf]

@ByAlu there is already a pr for this issue: #3739

[ZainlessBrombie]

On latest main (b3a2cbb):
thread 'main' panicked at 'Error while registering new asset type: "shader_material::CustomMaterial2" with UUID: f690fdae-d598-45ab-8225-97e2a3f056e0. Another type with the same UUID is already registered. Can not register new asset type with the same UUID', /tmp/bevy/crates/bevy_asset/src/asset_server.rs:110:13

I think this can be closed then?