Hmm. For context, I am using it for AWS IoT Shadows. They work by sending a delta between a "desired" and a "reported" json struct to a /delta topic, where some or all of the fields may or may not be (regular diff between jsons), thus the optional struct.

I am then doing something along the line of
```rust
fn apply_patch(&mut self, opt: Self::PatchState) {
    use ::miniconf::{TreeKey, JsonCoreSlash};

    // TODO: `MAX_KEY_LEN`, `MAX_VALUE_LEN`
    let mut buf = [0u8; 64];

    for path in Self::PatchState::nodes::<::miniconf::Path<heapless::String<64>, '/'>>() {
        let (path, node) = path.unwrap();
        assert!(node.is_leaf());

        match opt.get_json(path.as_str(), &mut buf) {
            Ok(len) if &buf[..len] != b"null" => {
                self.set_json(path.as_str(), &buf[..len]).unwrap();
            }
            _ => (),
        }
    }
}
```