Update data_model error at int or double cell

[gonojuarez]

I think this change solves the following error:

Error: Exception: null does not work for IntCellValue dart-sdk/lib/_internal/js_dev_runtime/private/ddcruntime/errors.dart 294:3 throw packages/excel/src/save/save_file.dart 124:16 packages/excel/src/save/save_file.dart 124:13 [_createCell] packages/excel/src/save/save_file.dart 997:16 [_updateCell] packages/excel/src/save/save_file.dart 652:9 [_setRows] packages/excel/src/save/save_file.dart 966:7 dart-sdk/lib/_internal/js_dev_runtime/private/linked_hash_map.dart 21:7 forEach packages/excel/src/save/save_file.dart 914:12 [_setSheetElements] packages/excel/src/save/save_file.dart 544:5 [_save] packages/excel/src/excel.dart 348:20

[FauconSpartiate]

@gonojuarez Can you add a test for this fix?

[gonojuarez]

sorry I can avoid this suggestion, I will download the code and find the bug, because I see the problem is related to the try-catch exception at class save_file I find this code :

    case DoubleCellValue():
        final String v = switch (numberFormat) {
          NumericNumFormat() => numberFormat.writeDouble(value),
          _ => throw Exception(
              '${numberFormat} does not work for ${value.runtimeType}'),
        };
        children = [
          XmlElement(XmlName('v'), [], [XmlText(v)]),
        ];
      case DateTimeCellValue():
        final String v = switch (numberFormat) {
          DateTimeNumFormat() => numberFormat.writeDateTime(value),
          _ => throw Exception(
              '${numberFormat} does not work for ${value.runtimeType}'),
        };
        children = [
          XmlElement(XmlName('v'), [], [XmlText(v)]),
        ];
      case DateCellValue():
        final String v = switch (numberFormat) {
          DateTimeNumFormat() => numberFormat.writeDate(value),
          _ => throw Exception(
              '${numberFormat} does not work for ${value.runtimeType}'),
        };
        children = [
          XmlElement(XmlName('v'), [], [XmlText(v)]),
        ];
      case TimeCellValue():
        final String v = switch (numberFormat) {
          TimeNumFormat() => numberFormat.writeTime(value),
          _ => throw Exception(
              '${numberFormat} does not work for ${value.runtimeType}'),
        };
        children = [
          XmlElement(XmlName('v'), [], [XmlText(v)]),
        ];
      case TextCellValue():
        children = [
          XmlElement(XmlName('v'), [], [
            XmlText(_excel._sharedStrings.indexOf(sharedString!).toString())
          ]),
        ];

    I am thinking that the numberFormat will be null and these throw the exception.

[FauconSpartiate]

Okay, you can open a new PR if you manage to fix the issue.