fix: allow passing empty namespace again for clusterResources

[dkoshkin]

A recent commit broke previous behavior of being able to collect clusterResources: {} from all namespaces.

From the docs

This will attempt to collect information from all namespaces

Tested with:

apiVersion: troubleshoot.sh/v1beta2
kind: SupportBundle
metadata:
  name: namespace-bug
spec:
  collectors:
    - clusterInfo: {}
    - clusterResources: {}

Ran it with this fix (see output snippet):

➜ tree support-bundle-2021-08-12T16_45_04/cluster-resources
support-bundle-2021-08-12T16_45_04/cluster-resources
├── deployments
│   ├── calico-system.json
│   ├── default.json
│   ├── kube-node-lease.json
│   ├── kube-public.json
│   ├── kube-system.json
│   ├── node-feature-discovery.json
│   └── tigera-operator.json

And with latest release

➜ ./support-bundle version
Replicated Troubleshoot 0.13.7
➜  tree support-bundle-2021-08-12T16_46_11/cluster-resources/
support-bundle-2021-08-12T16_46_11/cluster-resources/
├── deployments
│   └── default.json

[CLAassistant]

All committers have signed the CLA.

[xavpaice]

This has been over a year since submission, and I see that there are now several similar fixes in place already (though, not for the clusterResources collector).

I'll close this out now, if the issue is still current we should raise a clear bug and it's a simpler fix than this one.