Jira returns no project-specific custom date fields when creating Confluence Team Calendar event when more than one project is selected

Issue Summary

See https://jira.atlassian.com/browse/CONFSERVER-58368
This issue was reproduced integrating Confluence with Jira 8.0.3 with the Icalendar plugin upgraded to version 1.5.0.

When creating a Jira dates team calendar event in confluence, the custom date fields don't show when more than one project is selected.

Steps to Reproduce

1. In Confluence connect an Applink to Jira
2. In Jira, create two projects, "Project 1" and "Project 2".
3. In Jira, create a new custom field and configure as project-level to Project 1 and Project 2, rather than globally available.
4. Create a Jira issue in Project 1 with the custom date field.
5. In Confluence, create a new team calendar and add a Jira date event. Use the jql filter with 'Project in ("Project 1")' - the custom date field will show as an option to select.
6. Now change the query to 'Project in ("Project 1", "Project 2")' - the custom date field will not show even though it's available as a field in both projects

Expected Results

All custom date fields would show in the Team Calendar event creation dialog

Actual Results

When two or more projects are selected in a query, only global custom date fields are shown but not project-specific date fields.

Workaround

Create separate events for each project, to use the custom date field in the calendar.
OR
Make the custom date field global instead of project-restricted.