Fix guacEmpty being added into the ENT DB causing errors

[pxp928]

Description of the PR

fixes #2135

This PR also creates an Atlas migration that will fix this issue for any running instance of GUAC (ENT backend) if needed.

I did some testing locally and the migration works as intended.

PR Checklist

• All commits have a Developer Certificate of Origin (DCO) -- they are generated using -s flag to git commit.
• All new changes are covered by tests
• If GraphQL schema is changed, make generate has been run
• If GraphQL schema is changed, GraphQL client updates/additions have been made
• If OpenAPI spec is changed, make generate has been run
• If ent schema is changed, make generate has been run
• If collectsub protobuf has been changed, make proto has been run
• All CI checks are passing (tests and formatting)
• All dependent PRs have already been merged