message: chore: fix deepscan issues (remove redundant null checks)
diff: @@ -20,7 +20,7 @@ export function calculate_distance(node: AuspiceTreeNodeExtended, seq: AnalysisR
  })
  for (const qmut of seq.substitutions) {
  - const der = nodeSubstitutions?.get(qmut.pos)
  + const der = nodeSubstitutions.get(qmut.pos)
  if (der) {
  // position is also mutated in node
  if (qmut.queryNuc === der) {
  @@ -33,16 +33,14 @@ export function calculate_distance(node: AuspiceTreeNodeExtended, seq: AnalysisR
  // determine the number of sites that are mutated in the node but missing in seq.
  // for these we can't tell whether the node agrees with seq
  let undetermined_sites = 0
  - if (nodeSubstitutions) {
  for (const nmut of nodeSubstitutions) {
  const pos = nmut[0]
  if (!isSequenced(pos, seq)) {
  undetermined_sites += 1
  }
  }
  - }
  - const numMut = nodeSubstitutions?.size ?? 0
  + const numMut = nodeSubstitutions.size ?? 0
  // calculate distance from set overlaps.
  return numMut + seq.substitutions.length - 2 * shared_differences - shared_sites - undetermined_sites
  }
  