Fix get_property.

This was returning the error when a token was not an atom whereas we only wanted to check to see if it was the atom nil.

src/compare/util.rs

@@ -184,11 +184,8 @@ pub(crate) fn get_property<'b, 's, 'x>(
         .ok_or("Should have an attributes child.")?;
     let attributes_map = attributes_child.as_map()?;
     let prop = attributes_map.get(key).map(|token| *token);
-    match prop
-        .map(|token| token.as_atom())
-        .map_or(Ok(None), |r| r.map(Some))?
-    {
-        Some("nil") => return Ok(None),
+    match prop.map(|token| token.as_atom()) {
+        Some(Ok("nil")) => return Ok(None),
         _ => {}
     };
     Ok(prop)