Fix unpacking sboms issue from older Zarf packages (#1621)

## Description

This fixes an issue where SBOMs from older packages are not unpacked
correctly.

## Related Issue

Fixes #1610

## Type of change

- [X] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Other (security config, docs update, etc)

## Checklist before merging

- [X] Test, docs, adr added or updated as needed
- [X] [Contributor Guide
Steps](https://github.com/defenseunicorns/zarf/blob/main/CONTRIBUTING.md#developer-workflow)
followed

src/pkg/packager/inspect.go

@@ -73,10 +73,12 @@ func (p *Packager) Inspect(includeSBOM bool, outputSBOM string, inspectPublicKey
 
  if includeSBOM || outputSBOM != "" {
  // Extract the SBOM files from the sboms.tar file
- if err := archiver.Unarchive(p.tmp.SbomTar, p.tmp.Sboms); err != nil {
- return fmt.Errorf("unable to extract the SBOM files: %w", err)
+ _, tarErr := os.Stat(p.tmp.SbomTar)
+ if tarErr == nil {
+ if err := archiver.Unarchive(p.tmp.SbomTar, p.tmp.Sboms); err != nil {
+ return fmt.Errorf("unable to extract the SBOM files: %w", err)
+ }
  }
-
  }
 
  // Open a browser to view the SBOM if specified