Item._obj is not guaranteed to exist #542

This code has come up in a pytest-mypy issue because ._obj (which seems to be available publicly as .obj, btw) is not defined on MypyItems (custom pytest.Items used for running mypy on collected modules). Moreover, I don't know of a way to reasonably define it since MypyItems are not associated with any particular test function. That suggests that perhaps allure-pytest should be made to ignore such Items or, in this case, at least gracefully degrade into returning None when allure_title is called on them:

try:
    return item.obj.__allure_display_name__
except AttributeError:
    return None