id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
19616	QuerySet.__contains__ tries to check the length of a None	kalugny@…	nobody	"This is the code from QuerySet (version 1.42).
As you can see by the lines I've bolded, although _result_cache might be None, it is still being checked for len()

def __contains__(self, val):
        # The 'in' operator works without this method, due to __iter__. This
        # implementation exists only to shortcut the creation of Model
        # instances, by bailing out early if we find a matching element.
        pos = 0
        '''if self._result_cache is not None:'''
            if val in self._result_cache:
                return True
            elif self._iter is None:
                # iterator is exhausted, so we have our answer
                return False
            # remember not to check these again:
            pos = len(self._result_cache)
        '''else:'''
            # We need to start filling the result cache out. The following
            # ensures that self._iter is not None and self._result_cache is not
            # None
            it = iter(self)

        # Carry on, one result at a time.
        while True:
           ''' if len(self._result_cache) <= pos:'''
                self._fill_cache(num=1)"	Bug	new	Database layer (models, ORM)	1.4	Normal				Unreviewed	0	0	0	0	1	0