Added a test to ensure bad assignation to M2M doesn't clear data

        # causes a TypeError in add_lazy_relation

        m1 = RegressionModelSplit(name='1')

        m1.save()

    def test_assigning_invalid_data_to_m2m_doesnt_clear_existing_relations(self):

        t1 = Tag.objects.create(name='t1')

        t2 = Tag.objects.create(name='t2')

        c1 = TagCollection.objects.create(name='c1')

        c1.tags = [t1, t2]

        with self.assertRaises(TypeError):

            c1.tags = 7

        c1.refresh_from_db()

        self.assertQuerysetEqual(c1.tags.order_by('name'), ["<Tag: t1>", "<Tag: t2>"])