Panic duric transform - null for loop

[deevyansh]

Description

The null in the for expression gives the panic during transform.

Steps to Reproduce

1. The following code to be included in the main.rs

use jslt::Jslt;
use serde_json::json;
use std::fs;
fn main() -> Result<(), Box <dyn std::error::Error> > {
  let jslt: Jslt = r#"
[for(null) . ]
  "#.parse()?;
  let input = json!({
    "data": [
       [1, 2, 3, 4, 5],
       [6, 7, 8, 9, 10]
    ]
  });
  let output = jslt.transform_value(&input)?;
  println!("{}",output);
  assert_eq!("null",output.to_string());
  Ok(())
}

Actual Output

thread 'main' panicked at jslt_dev/jslt/src/transform/value/array.rs:81:18:
Should be array

Expected Output

null

Environment

Nightly Rust Toolchain