Fix/capability transient migration

[circlecube]

Proposed changes

Temporary hook to filter the capabilities in case they are empty.
This is to fix an issue where the migration value is not found on new sites.
This temporary fix is needed to keep things working while determining the root cause.

See PRESS0-1827

Type of Change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

Checklist

• I have read the CONTRIBUTING doc
• Linting and tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

Further comments

[circlecube]

Recreated this PR after changing the branch name to match the expected convention (fix not hotfix) so it would build the plugin.