导出提醒An item with the same key has already been added. 但是model里并没有重复的字段名

### Expected behaviour
导出提醒：An item with the same key has already been added. Key: Milestone Status
导出Model截图：

### Actual behaviour
An item with the same key has already been added. Key: Milestone Status
在 System.ThrowHelper.ThrowAddingDuplicateWithKeyArgumentException[T](T key)
在 System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
在 OfficeOpenXml.Table.ExcelTableColumnCollection..ctor(ExcelTable table)
在 OfficeOpenXml.ExcelWorksheet.DeleteColumn(Int32 columnFrom, Int32 columns)
在 Magicodes.ExporterAndImporter.Excel.Utility.ExportHelper`1.DeleteIgnoreColumns()
在 Magicodes.ExporterAndImporter.Excel.Utility.ExportHelper`1.AddHeaderAndStyles()
在 Magicodes.ExporterAndImporter.Excel.ExcelExporter.ExportAsByteArray[T](ICollection`1 dataItems)
在 Magicodes.ExporterAndImporter.Excel.ExcelExporter.d__5`1.MoveNext()

#### package versions
Magicodes.IE.Core, Version=2.6.7.0