[infra] Handle test steps with no tested configuration
[infra] Handle test steps with no tested configuration

Change-Id: I95543f88a64884bf2334165baa986d381bbf7872
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/141241
Commit-Queue: Karl Klose <49bc0b76cffb0b10cd8c84f9cabc97a31ffe6343@google.com>
Reviewed-by: Karl Klose <49bc0b76cffb0b10cd8c84f9cabc97a31ffe6343@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk