Incorrect type narrowing on union of `TypedDict`

from typing import Any, TypedDict

class _SessionData(TypedDict):
    created: int
    session: dict[str, Any]


class _EmptyDict(TypedDict):
    """Empty dict for typing."""


SessionData = _SessionData | _EmptyDict

data: SessionData

reveal_type(data)
a = data if data else None
reveal_type(a)

aiohttp_session/__init__.py:56: note: Revealed type is "Union[TypedDict('aiohttp_session._SessionData', {'created': builtins.int, 'session': builtins.dict[builtins.str, Any]}), TypedDict('aiohttp_session._EmptyDict', {})]"
aiohttp_session/__init__.py:58: note: Revealed type is "Union[TypedDict('aiohttp_session._EmptyDict', {}), None]"

I also get the same result if I make it not data. The _SessionData type just disappears for no reason and it keeps saying the empty dict will be the result regardless of the boolean check.

Start by running the provided TypedDict union example and checking the two reveal_type results reported from aiohttp_session/init.py. Trace mypy's boolean narrowing for the union and verify that both the non-empty and empty TypedDict branches are handled correctly for both data and not data.