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The error "AttributeError: 'NoneType' object has no attribute..." probably means that you attempted to retrieve an object (such as a person, or family) by using its internal handle, but the database can't find it. Likely, the object is still there, but the internal database references have gotten corrupted.
To fix, first, make a Gramps XML backup.
Then, you need to run the menu -> Tools -> Family Tree Repair and run the tools: