call_fn inside with_engine caused deadlock

```rust
fn call_lua_on_update_from_rust(
mut scripted_entities: Query<(Entity, &mut LuaScriptData)>,
scripting_runtime: ResMut,
mut exit: EventWriter,
) {
for (entity, mut script_data) in &mut scripted_entities {
scripting_runtime.with_engine(|engine| {
let val = scripting_runtime
.call_fn("get_value", &mut script_data, entity, ())
.unwrap()
.0;
println!(
"script returned: {}",
engine.registry_value::(&val).unwrap()
);
});
exit.write(AppExit::Success);
}
}
```
Caused deadlock

No file or test is named. Start by reproducing the shown call_fn inside with_engine example and tracing the locking interaction; done means the call no longer deadlocks while preserving the demonstrated script result and exit behavior.

Written by the indexing model from the issue text.