[release/1.7] Fix issue with empty host tree in hosts.toml

[brandond]

Fixes: #10027

[k8s-ci-robot]

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[dmcgowan]

Seems the issue here would be better fixed by just changing getSortedhosts to return an empty list in that case. What is root.Get("host") returning when you provide it the [host] config? It seems that code should handle root.Get("host") returning nil, but is that what it sees.

[brandond]

Seems the issue here would be better fixed by just changing getSortedhosts to return an empty list in that case.

Sure, that'd work too. It didn't seem like there was much point in calling getSortedHosts at all if there are no HostConfigs in the first place, but what you're suggesting is probably a slightly less involved change.

What is root.Get("host") returning when you provide it the [host] config?

I don't know, I didn't poke at the toml parser return; I suspect it just returns an empty tree so that list := append([]string{}, iter.Keys()...) just ends up creating an empty list, which is what gets returned.

[dmcgowan]

Note this fix is not needed in main as we have bumped the toml library major version and the new implementation does not have this issue.