title: is it possible to let List validation not set value when using poi to export to excel
body: <p>I am using poi <code>poi-ooxml-4.0.0</code> to export an excel in the spring boot java project, but shows error:</p>
  <pre><code>Caused by: java.lang.IllegalArgumentException: List validation with explicit values must specify at least one value
      at org.apache.poi.xssf.usermodel.XSSFDataValidationConstraint.&lt;init&gt;(XSSFDataValidationConstraint.java:50) ~[poi-ooxml-4.0.0.jar!/:4.0.0]
      at org.apache.poi.xssf.usermodel.XSSFDataValidationHelper.createExplicitListConstraint(XSSFDataValidationHelper.java:66) ~[poi-ooxml-4.0.0.jar!/:4.0.0]
      at com.sportswin.soa.zhuolianorg.repo.DataValidationHandler.lambda$afterSheetCreate$3(DataValidationHandler.java:67) ~[classes!/:na]
      at java.util.HashMap.forEach(HashMap.java:1289) ~[na:1.8.0_252]
      at com.sportswin.soa.zhuolianorg.repo.DataValidationHandler.afterSheetCreate(DataValidationHandler.java:61) ~[classes!/:na]
      at com.alibaba.excel.util.WriteHandlerUtils.afterSheetCreate(WriteHandlerUtils.java:103) ~[easyexcel-2.2.11.jar!/:na]
      at com.alibaba.excel.util.WriteHandlerUtils.afterSheetCreate(WriteHandlerUtils.java:93) ~[easyexcel-2.2.11.jar!/:na]
      at com.alibaba.excel.context.WriteContextImpl.initSheet(WriteContextImpl.java:188) ~[easyexcel-2.2.11.jar!/:na]
      at com.alibaba.excel.context.WriteContextImpl.currentSheet(WriteContextImpl.java:122) ~[easyexcel-2.2.11.jar!/:na]
      at com.alibaba.excel.write.ExcelBuilderImpl.addContent(ExcelBuilderImpl.java:53) ~[easyexcel-2.2.11.jar!/:na]
      at com.alibaba.excel.ExcelWriter.write(ExcelWriter.java:161) ~[easyexcel-2.2.11.jar!/:na]
      at com.alibaba.excel.ExcelWriter.write(ExcelWriter.java:146) ~[easyexcel-2.2.11.jar!/:na]
      at com.sportswin.soa.zhuolianorg.repo.UploadSparkUserDAO.addRemark(UploadSparkUserDAO.java:103) ~[classes!/:na]
  </code></pre>
  <p>the error is clear that tell me the List validation column value must set, but sometimes the data validation column did not have data, is it possible to output the excel without default value? like this:</p>
  <p><a href="https://i.stack.imgur.com/3upFh.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/3upFh.png" alt="enter image description here" /></a></p>