🐛 fix: skip port deletion when instances have no port

[dulek]

What this PR does / why we need it:
This adds a condition in GarbageCollectErrorInstancesPort to avoid index outOfRange error when an instance has no port because of some reason (maybe the instance provisioning failed because of infra issue).

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #1805

Special notes for your reviewer:

1. Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

TODOs:

• squashed commits
• if necessary:
  • adds unit tests

/hold

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[dulek]

This is a replacement for #1794.

[dulek]

And I added a simple unit test covering this case too.

[EmilienM]

/lgtm

Note, I'll port that to the port refactor.

[EmilienM]

well in fact I don't need to port that PR into #1788 because the ports management is now separated from instances.

[jichenjc]

/approve

I seems saw similar PR for same purpose recently but can't find where it is ..
anyway, the PR lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dulek, jichenjc

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[mdbooth]

/hold cancel