def METHOD_NAME(self) -> None:
    """Invalid data ends up clearing out the ignored users list."""
    # Add some data and ensure it is there.
    self._update_ignore_list("@other:test")
    self.assert_ignored(self.user, {"@other:test"})
    self.assert_ignorers("@other:test", {self.user})
    # No ignored_users key.
    self.get_success(
        self.store.add_account_data_for_user(
            self.user,
            AccountDataTypes.IGNORED_USER_LIST,
            {},
        )
    )
    # No one ignores the user now.
    self.assert_ignored(self.user, set())
    self.assert_ignorers("@other:test", set())
    # Add some data and ensure it is there.
    self._update_ignore_list("@other:test")
    self.assert_ignored(self.user, {"@other:test"})
    self.assert_ignorers("@other:test", {self.user})
    # Invalid data.
    self.get_success(
        self.store.add_account_data_for_user(
            self.user,
            AccountDataTypes.IGNORED_USER_LIST,
            {"ignored_users": "unexpected"},
        )
    )
    # No one ignores the user now.
    self.assert_ignored(self.user, set())
    self.assert_ignorers("@other:test", set())