Investigate NPE from ES-2889

Customer has just upgraded and lost the applinks, they're restoring, they're asking for assistance about an NPE which is scoped to a small feature.

Diagnosis

Confluence reaches out to Jira, but Jira doesn’t recognize the applink id based on the URL, so Jira doesn’t provide the api_supported_version and Confluence assumes it will be present.

It didn’t cause an error earlier, probably because Atlassian had another implementation/version of Apache’s MutableInt.

Stacktrace