Description of problem:
While syncing Red Hat Enterprise Linux Atomic Host Trees x86_64, the task fails with:
Output:
Branches updated
Errors:
undefined method `to_datetime' for nil:NilClass

Version-Release number of selected component (if applicable):
Satellite 6.5.0 Snap 20
This may be a regressions form snap 19

How reproducible:
Always

Steps to Reproduce:
1. Upload a manifest that provides Red Hat Enterprise Linux Atomic Host Trees x86_64
2. Enable Red Hat Enterprise Linux Atomic Host Trees x86_64
3. Synchronize Red Hat Enterprise Linux Atomic Host Trees x86_64

Actual results:
Output:
Branches updated
Errors:
undefined method `to_datetime' for nil:NilClass

Expected results:
The repository sync completes successfully.