message: now uses unwrap_or_default()
diff: @@ -196,10 +196,7 @@ impl Variables {
  .map_err(|cause| Error::InvalidHex(variable.into(), cause))?;
  Ok((c as char).to_string().into())
  }
  - Some(("env", variable)) => match env::var(variable) {
  - Ok(v) => Ok(v.into()),
  - Err(_) => Ok("".into()),
  - },
  + Some(("env", variable)) => Ok(env::var(variable).unwrap_or_default().into()),
  Some(("super", _)) | Some(("global", _)) | None => {
  // Otherwise, it's just a simple variable name.
  match self.get(name) {
  