message: fix: ensure insertion start is set correctly
diff: @@ -25,15 +25,13 @@ pub fn strip_insertions<T: Letter<T>>(qry_seq: &[T], ref_seq: &[T]) -> StripInse
  for i in 0..ref_seq.len() {
  let c = ref_seq[i];
  - if c == T::GAP {
  - current_insertion.push(qry_seq[i]);
  + if c.is_gap() {
  if current_insertion.is_empty() {
  // NOTE: by convention we set position of insertion to be the index of a character that precedes the insertion,
  // i.e. a position of reference nucleotide *after* which the insertion have happened.
  insertion_start = ref_pos;
  - } else {
  - current_insertion.push(qry_seq[i]);
  }
  + current_insertion.push(qry_seq[i]);
  } else {
  qry_stripped.push(qry_seq[i]);
  ref_pos += 1;
  