Fix: leaf_level offloading breaks after delete_adapters

[adi776borate]

What does this PR do?

Fixes #12396

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline?
• Did you read our philosophy doc (important for complex PRs)?
• Discussed in the issue Using leaf_level together with delete_adapters can get some errors. #12396.
• Did you make sure to update the documentation with your changes? Here are the
  documentation guidelines, and
  here are tips on formatting docstrings.
• Did you write any new necessary tests?

Who can review?

@yiyixuxu
@sayakpaul
Anyone in the community is free to review the PR once the tests have passed.