message: Avoid allocating Vec every time we add to reference cache
diff: @@ -530,7 +530,7 @@ impl<'arena, 'env, 'data> Context<'arena, 'env, 'data> {
  // Store the parsed reference in the reference cache
  self.cached_refs
  .entry(pos)
  - .or_insert(Vec::with_capacity(1))
  + .or_insert_with(|| Vec::with_capacity(1))
  .push(ParsedRef {
  format: format.clone(),
  expr: expr.clone(),
  