ruby – Spreadsheet gem：无法创建空工作簿

我有代码迭代一个集合,并在每个项目的同一工作簿中创建一个工作表.当集合为空时,执行的代码最终看起来像：

io = StringIO.new
book = Spreadsheet::Workbook.new
book.write(io)

最后一行提出：

TypeError: can't convert nil into Integer
    spreadsheet/excel/writer/workbook.rb:636:in `pack'
    spreadsheet/excel/writer/workbook.rb:636:in `write_window1'
    spreadsheet/excel/writer/workbook.rb:419:in `write_from_scratch'
    spreadsheet/excel/writer/workbook.rb:644:in `write_workbook'
    spreadsheet/writer.rb:12:in `write'
    spreadsheet/workbook.rb:124:in `write'

将我的代码更改为此修复了一些事情：

io = StringIO.new
book = Spreadsheet::Workbook.new
book.create_worksheet if book.worksheets.empty?
book.write(io)

但我宁愿不必包含对create_worksheet的调用.我的问题是：

a)我的代码中有什么问题吗？

b)这是宝石中的一个错误还是预期崩溃？