code: function lastNonEmptyLine (linesArray) {
    let idx = linesArray.length - 1
  
    while (idx >= 0 && !linesArray[idx]) {
      idx--
    }
  
    return idx
  }
docs: Get the last non empty line number.
  
  @private
  @param  {Array<String>} linesArray - All the lines.
  @return {Number} - The number of the last non empty line.