Reflection Issue with petgraph::graph::DiGraph

## Bevy version

0.15.0

## What you did

I'm working on implementing scripting support using bevy\_reflect.

## What went wrong

There's something weird going on with `petgraph::graph::DiGraph`:

```rs
OpaqueInfo {
ty: petgraph::graph::DiGraph,
generics: Generics(
[],
),
docs: None,
}
```

This type clearly has generic parameters, but the generics field is empty.

## Additional information

The reflection is implemented using the macro `impl_reflect_opaque!`, maybe something there goes wrong.