fix(xo-server/Rolling Pool Update/_xcpUpdate): handle undefined hosts

[pdonias]

Fixes #6170
Introduced by e7f9111

Check list

Check if done, if not relevant leave unchecked.

• PR reference the relevant issue (e.g. Fixes #007 or See xoa-support#42)
• if UI changes, a screenshot has been added to the PR
• documentation updated
• CHANGELOG.unreleased.md:
  • enhancement/bug fix entry added
  • list of packages to release updated (${name} v${new version})
• I have tested added/updated features (and impacted code)
  • unit tests (e.g. cron/parse.spec.js)
  • if xo-server API changes, the corresponding test has been added to/updated on xo-server-test
  • at least manual testing

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[olivierlambert]

Does it also fix the issue if you try to update from "Install pool patches" button?

[pdonias]

Yes.

[rauly1994]

since i'm new to xen server. in this case. what would i need to do in order to fix the issue. is there an update i need to run?

[olivierlambert]

If you are using XOA, just click on "update" button in the XOA updater section.
If you are using XO from the sources, follow the doc: https://xen-orchestra.com/docs/installation.html#updating