[3.7] bpo-33041: Add missed error checks when compile "async for" (GH-6053) (GH-6060)

and remove redundant code.
(cherry picked from commit 67ee07795bcd84b679c000780212d4d81a1490a3)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
1 file changed