Caused by: java.lang.NullPointerException: Cannot invoke "java.awt.Color.getRGB()" because "color" is null
at org.ttzero.excel.entity.style.ColorIndex.indexOf(ColorIndex.java:54)
at org.ttzero.excel.entity.style.Border.writeProperties(Border.java:561)
at org.ttzero.excel.entity.style.Border.toDom(Border.java:478)
at org.ttzero.excel.entity.style.Styles.writeTo(Styles.java:568)
at org.ttzero.excel.entity.e7.XMLWorkbookWriter.writeGlobalAttribute(XMLWorkbookWriter.java:181)
at org.ttzero.excel.entity.e7.XMLWorkbookWriter.createTemp(XMLWorkbookWriter.java:416)
at org.ttzero.excel.entity.e7.XMLWorkbookWriter.writeTo(XMLWorkbookWriter.java:124)
at org.ttzero.excel.entity.Workbook.writeTo(Workbook.java:712)