Affected: Go: helm.sh/helm/v3

A Helm contributor discovered an improper validation of type error when parsing Chart.yaml and index.yaml files that can lead to a panic.

### Impact

There are two areas of YAML validation that were impacted. First, when a `Chart.yaml` file had a `null` maintainer or the `child` or `parent` of a dependencies `import-values` could be parsed as something other than a string, `helm lint` would panic. Second, when an `index.yaml` had an empty entry in the list of chart versions Helm would panic on interactions with that repository.

### Patches

This issue has been resolved in Helm v3.18.5.

### Workarounds

Ensure YAML files are formatted as Helm expects prior to processing them with Helm.

### References

Helm's security policy is spelled out in detail in our [SECURITY](https://github.com/helm/community/blob/master/SECURITY.md) document.

### Credits

Disclosed by Jakub Ciolek at AlphaSense.