message: perf: shortcut return proposal reward when target_proposals is empty
diff: @@ -211,7 +211,7 @@ impl<'a, CS: ChainStore<'a>> RewardCalculator<'a, CS> {
  }
  }
  - while index.number() > competing_commit_start {
  + while index.number() > competing_commit_start && !target_proposals.is_empty() {
  index = store
  .get_block_header(&index.data().raw().parent_hash())
  .expect("header stored");
  