https://bugzilla.wikimedia.org/show_bug.cgi?id=69664
--- Comment #2 from Fabian CommodoreFabianus@gmx.de --- Currently I see there two “easy” fixes: One way to fix it would be in the second step to look either if text is a str/unicode.
The second would be to check if page is not a WikibasePage. But that one would break as soon as another Page subclass is introduced which also hasn't a text. Maybe it doesn't make sense that Wikibase is a subclass of Page, because the value stored internally are very different (but that now a bit late, because it's in the API now).
I'm not sure how redirects work actually. Would they return a string?