Code:
[__NSCFDictionary setObject:forKey:]: attempt to insert nil value (key: date)
5 ISS Viewer 0x0000452a -[Parser parser:didEndElement:namespaceURI:qualifiedName:] + 594
At the end of some tag in the XML you're trying to insert a nil object into the dictionary for the key "date". I'd look out the code where you're adding the date to the dictionary and find out why the date is nil.
You'll have to either create some dummy date to insert, or just don't insert the date if it's nil.