Incorrect deserialization of triply-nested elements with a default namespace

[av-gal]

I've encountered an issue with the yaserde_derive feature where a grandchild of the namespaced root node is not being deserialised. The child and grandchild nodes are both deserialised correctly when they are processed separately, without the root node as their ancestor.

Test case:

use yaserde::YaDeserialize;

#[derive(YaDeserialize, Debug, PartialEq)]
#[yaserde(rename = "EBMLSchema", namespace = "some_namespace")]
struct Schema {
  #[yaserde(rename = "element")]
  elements: Vec<Element>,
}

#[derive(YaDeserialize, Debug, PartialEq)]
#[yaserde(rename = "element")]
struct Element {
  #[yaserde(rename = "documentation")]
  documentation: Vec<Documentation>,
}

#[derive(YaDeserialize, Debug, PartialEq)]
#[yaserde(rename = "documentation")]
struct Documentation {
  #[yaserde(text)]
  body: String,
}

#[test]
fn nested_element_equality() {
  let parent = r#"<EBMLSchema xmlns="some_namespace">
<element>
<documentation>Test</documentation>
</element>
</EBMLSchema>"#;
  let parent: Schema = yaserde::de::from_str(parent).unwrap();

  let child = r#"<element>
<documentation>Test</documentation>
</element>"#;
  let child: Element = yaserde::de::from_str(child).unwrap();

  assert_eq!(parent.elements[0], child);
}

Output:

thread 'nested::nested_element_equality' panicked at examples\src\nested.rs:38:3:
assertion `left == right` failed
  left: Element { documentation: [] }
 right: Element { documentation: [Documentation { body: "Test" }] }
stack backtrace:
   0: std::panicking::begin_panic_handler
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library/std\src\panicking.rs:662
   1: core::panicking::panic_fmt
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library/core\src\panicking.rs:74
   2: core::panicking::assert_failed_inner
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library/core\src\panicking.rs:412
   3: core::panicking::assert_failed<yaserde_examples::nested::Element,yaserde_examples::nested::Element>
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library\core\src\panicking.rs:367
   4: yaserde_examples::nested::nested_element_equality
             at .\src\nested.rs:38
   5: yaserde_examples::nested::nested_element_equality::closure$0
             at .\src\nested.rs:25
   6: core::ops::function::FnOnce::call_once<yaserde_examples::nested::nested_element_equality::closure_env$0,tuple$<> >
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library\core\src\ops\function.rs:250
   7: core::ops::function::FnOnce::call_once
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library/core\src\ops\function.rs:250

[MarcAntoine-Arnaud]

I have updated the code to fix namespace definition and usage.
It's added as an example with the commit 3b45f08