steps to reproduce

1. load the attached file

current result

java.lang.IllegalArgumentException: null rgb array
at org.zkoss.zss.model.impl.ColorImpl.<init>(ColorImpl.java:42)
at org.zkoss.zss.range.impl.imexp.ExcelXlsxImporter.prepareColorScale(ExcelXlsxImporter.java:958)
at org.zkoss.zss.range.impl.imexp.ExcelXlsxImporter.prepareConditonalFormattingRuleImpl(ExcelXlsxImporter.java:879)
at org.zkoss.zss.range.impl.imexp.ExcelXlsxImporter.prepareConditionalFormattingImpl(ExcelXlsxImporter.java:847)
at org.zkoss.zss.range.impl.imexp.ExcelXlsxImporter.importConditionalFormatting(ExcelXlsxImporter.java:829)
at org.zkoss.zss.range.impl.imexp.AbstractExcelImporter.importSheet(AbstractExcelImporter.java:397)
at org.zkoss.zss.range.impl.imexp.AbstractExcelImporter.imports(AbstractExcelImporter.java:154)
at org.zkoss.zss.range.impl.imexp.ExcelImportAdapter.imports(ExcelImportAdapter.java:46)
at org.zkoss.zss.range.impl.imexp.AbstractImporter.imports(AbstractImporter.java:54)
at org.zkoss.zss.ui.Spreadsheet.getSBook(Spreadsheet.java:653)
at org.zkoss.zss.ui.Spreadsheet.getSelectedSSheet(Spreadsheet.java:851)
at org.zkoss.zss.ui.Spreadsheet.doInvalidate(Spreadsheet.java:5465)
at org.zkoss.zss.ui.Spreadsheet.invalidate(Spreadsheet.java:4314)
at org.zkoss.zss.ui.Spreadsheet.setSrc(Spreadsheet.java:891)

root cause

• zss doesn't support theme color
  

debug info

• ctColor value is <xml-fragment theme="8" tint="-0.249977111117893" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships"/>