Calling server function with empty vector argument causes a crash

[patrik-cihal]

Problem

Happens on 0.6.1. When server function that accepts vector argument is called where it is an empty vector it cause 500 error.
The issue is that the argument doesn't get passed in the http request as

arg: []

but rather ommited completely which makes the server arguments fail to deserialize.

Steps To Reproduce

Steps to reproduce the behavior:
This the minimal code:

use dioxus::prelude::*;

fn main() {
    dioxus::launch(App);
}

#[component]
fn App() -> Element {
    rsx! {
        button {
            onclick: move |_| {
                async move {
                    // This will fail because empty vector is not properly serialized
                    let result = s_f(vec![]).await;
                    println!("Result: {:?}", result);
                }
            },
            "Test empty vector"
        }
        button {
            onclick: move |_| {
                async move {
                    // This will work because vector has an item
                    let result = s_f(vec!["Hello world".into()]).await;
                    println!("Result: {:?}", result);
                }
            },
            "Test non-empty vector"
        }
    }
}

#[server(SF)]
async fn s_f(items: Vec<String>) -> Result<String, ServerFnError> {
    println!("Items: {:?}", items);
    Ok("Success".into())
} 

Expected behavior

Screenshots

Environment:

• Dioxus version: 0.6.1
• Dioxus platform: Web
• Browser: Firefox