If the Cell has no defined style, return the default style of the Workbook.
For example if a cell is formatted under the "General" category, its style instead of being General it ended up being 'Null'.
This PR adds defines the Cell style to the Workbooks default as Excel does.
If the Cell has no defined style, return the default style of the Workbook.
For example if a cell is formatted under the "General" category, its style instead of being General it ended up being 'Null'. This PR adds defines the Cell style to the Workbooks default as Excel does.