As serhiy pointed out in a comment in PR 3924, setting self->text or self->tail to
NULL might lead to an assertion failure, so we should also prevent the following
assertion failure (and the similar one for tail):
import xml.etree.ElementTree
class X:
    def __del__(self):
        elem.text
        
elem = xml.etree.ElementTree.Element('elem')
elem.text = X()
elem.__setstate__({'tag': None}) # implicitly also set elem.text to None