Checklist

• I have verified that the issue exists against the master branch of Celery.
• This has already been asked to the discussion group first.
• 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

• Preserve callbacks when replacing a task with a chain #6189

Possible Duplicates

• None

Environment & Settings

Celery version: 5.0.1 (singularity)

software -> celery:5.0.1 (singularity) kombu:5.0.2 py:3.9.0
            billiard:3.6.3.0 py-amqp:5.0.1
platform -> system:Linux arch:64bit, ELF
            kernel version:5.8.0-26-generic imp:CPython
loader   -> celery.loaders.default.Loader
settings -> transport:amqp results:disabled

deprecated_settings: None

Steps to Reproduce

Required Dependencies

• Minimal Python Version: N/A or Unknown
• Minimal Celery Version: 4.x
• Minimal Kombu Version: N/A or Unknown
• Minimal Broker Version: N/A or Unknown
• Minimal Result Backend Version: N/A or Unknown
• Minimal OS and/or Kernel Version: N/A or Unknown
• Minimal Broker Client Version: N/A or Unknown
• Minimal Result Backend Client Version: N/A or Unknown

Python Packages

Other Dependencies

Minimally Reproducible Test Case

from celery import shared_task, chain

@shared_task
def foo(*args):
  return 'foo'

@shared_task(bind=True)
def replace_with_empty_chain():
  self.replace(chain())

chain(foo.s(), replace_with_empty_chain.s()).delay()

Expected Behavior

A clear error message is raised.

Actual Behavior

An IndexError is raised with a message that doesn't explain what went wrong.