Fixed an Issue Where Copying a Registration Template With Registration Attributes Would Break Registrations

Proposed Changes

Fixes a bug in the Registration Template Detail that caused incomplete attributes to be added to the attribute cache. These incomplete attributes cause the Obsidian Registration Entry block to throw a null reference exception whenever it tried to load a registration template's details.

This fixes that issue by removing attributes with an ID of 0 from the attribute cache right after they are added to the cache.

Fixes: #5823

Types of changes

What types of changes does your code introduce to Rock? Put an x in the boxes that apply

[x] Bugfix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality, which has been approved by the core team)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

[x] This is a single-commit PR. (If not, please squash your commit and re-submit it.)
[x] I verified my PR does not include whitespace/formatting changes -- because if it does it will be closed without merging.
[x] I have read the Contributing to Rock doc
[x] By contributing code, I agree to license my contribution under the Rock Community License Agreement
[x] Unit tests pass locally with my changes
[x] I have added any required unit tests or integration tests that prove my fix is effective or that my feature works
[x] I have included updated language for the Rock Documentation (if appropriate)

SparkDevNetwork / Rock