hartez has uploaded a patch.
Description:
This addresses two possible sources of NullReferenceExceptions when opening a file:
1. A Null WorkbookStylesPart - this is the problem when opening the example file provided by FirebirdUK in issue #8631.
2. Null WorkbookProperties object when looking for the Date1904 setting - I encountered this in Excel files output by ActiveReports (which is what led me to look at this issue in the first place).