CONTAINER1015 does not contain the registry name

[Falco20019]

Describe the bug

Instead of the registry name, the CONTAINER1015 message only shows an empty string.

To Reproduce

1. Use ContainerBaseImage with an unknown image
2. Check the error message

Further technical details

This was introduced with 6eeea6c and affects the following builds:

• 9.0.103+
• 9.0.200+
• 9.0.300+
• 10.0.100-preview.1+

Strings.RepositoryNotFound expects the repository name to be {2} but due to the change it's now {3}. {2} is now the base image digest instead.