address another nil ptr check in podmanFactory.CanHandleAndAccept()

[char8]

We ran into the same issue as #3464, but adding the check against cntr.State was insufficient to prevent the nil ptr panic.

The ContainerJSON type returned by InspectContainer embeds a ptr to ContainerJSONBase, and it seemed this ptr was nil in the return, leading cadvisor to crash loop on startup.

I haven't looked into the specific JSON response podman is returning to trigger this, so there's potentially a bug in the podman API itself where it returned a nil error and an empty payload in response to the inspect call.

I do see the podman daemon returning 500 error codes for some inspect queries, and it appears validateResponse (container/podman/podman.go:41) doesn't handle 5xx status codes? so that may be the underlying issue here - podman returns a 5xx and empty body, and the json decoder unmarshals it to a nil.

Happy to add handling for 5xx to this PR as an added measure if that is appropriate.

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[iwankgb]

/ok-to-test

[char8]

CLA signed - sorry for the delay