Checklist

• I have read the relevant section in the
  contribution guide
  on reporting bugs.
• I have checked the issues list
  for similar or identical bug reports.
• I have checked the pull requests list
  for existing proposed fixes.
• I have checked the commit log
  to find out if the bug was already fixed in the master branch.
• I have included all related issues and possible duplicate issues
  in this issue (If there are none, check this box anyway).

Mandatory Debugging Information

• I have included the output of celery -A proj report in the issue.
  (if you are not able to do this, then at least specify the Celery
  version affected).
• I have verified that the issue exists against the master branch of Celery.
• I have included the contents of pip freeze in the issue.
• I have included all the versions of all the external dependencies required
  to reproduce this bug.

Optional Debugging Information

• I have tried reproducing the issue on more than one Python version
  and/or implementation.
• I have tried reproducing the issue on more than one message broker and/or
  result backend.
• I have tried reproducing the issue on more than one version of the message
  broker and/or result backend.
• I have tried reproducing the issue on more than one operating system.
• I have tried reproducing the issue on more than one workers pool.
• I have tried reproducing the issue with autoscaling, retries,
  ETA/Countdown & rate limits disabled.
• I have tried reproducing the issue after downgrading
  and/or upgrading Celery and its dependencies.

Related Issues and Possible Duplicates

Related Issues

• None

Possible Duplicates

• Subsequent groups within a chain fail Subsequent groups within a chain fail #3585
• Consecutive groups in chain fails Consecutive groups in chain fails #4848
• task/group chains fails in some scenarios task/group chains fails in some scenarios #5467

Environment & Settings

Celery version: 4.3.0

Steps to Reproduce

Minimally Reproducible Test Case

from celery import  group, chain
from tasks import task as t

# failing sequence
task = group([ t.si(),t.si(), chain( t.si(), group([ t.si(), t.si()]))])

# working sequence
task = group([ t.si(),t.si(), chain( t.si(), group([ t.si(), t.si()]), t.si())])

async_result = task.apply_async()
result = async_result.get()

Expected Behavior

Calling get return group result.

Actual Behavior

All task finish success but calling .get() fail with traceback:

Traceback (most recent call last):
  File "/my_app.py", line 111, in add_to_queue
    result = async_result.get()
  File "/root/.cache/pypoetry/virtualenvs/my_app/lib/python3.7/site-packages/celery/result.py", line 697, in get
    on_interval=on_interval,
  File "/root/.cache/pypoetry/virtualenvs/my_app/lib/python3.7/site-packages/celery/result.py", line 815, in join_native
    on_message, on_interval):
  File "/root/.cache/pypoetry/virtualenvs/my_app/lib/python3.7/site-packages/celery/backends/asynchronous.py", line 137, in iter_native
    if node._cache:
AttributeError: 'GroupResult' object has no attribute '_cache'