Description of problem: If some of DATA_SOURCE_* parameters are set in Template, then creation flow stucks with error: "Error "DataSource val/_____ does not exist" for field "spec.dataVolumeTemplates[0]"."

Version-Release number of selected component (if applicable): KCP v4.12.0-149

How reproducible: always

Steps to Reproduce:
1. Clone a Template
2. In cloned Template set as required DATA_SOURCE_NAME or DATA_SOURCE_NAMESPACE or both and save
3. Start VM creation flow from clobed Template in Catalog
4. Click Customize VirtualMachine

Actual results: Error message appears

Expected results: Creation flow continues

Additional info: