UnivariateTimeSeries.inverseDifferencesAtLag calculates return value which is never used

[rbraley]

def inverseDifferencesAtLag(
      diffedTs: Vector,
      destTs: Vector,
      lag: Int,
      startIndex: Int): Vector = {
    require(startIndex >= lag, "starting index cannot be less than lag")
    val addedTs = if (destTs == null) diffedTs.copy else destTs
    if (lag == 0) {
      addedTs
    } else {
      val n = diffedTs.size
      var i = 0

      val arr = addedTs.toArray
      while (i < n) {
        // elements prior to starting point are copied over without modification
        arr(i) = if (i < startIndex) diffedTs(i) else diffedTs(i) + addedTs(i - lag)
        i += 1
      }
      addedTs
    }
  }

here arr is never used