Default IssueFilters instance shouldn't exclude any issues

[terrajobst]

A default instance of IssueFilter has all properties set to null, which in the resulting graph query will compare all the fields to null. However, this means it looks for issues which have no milestone and no assignee. Since "*" includes all issues, I suggest that IssueFilter initializes Milestone and Assignee to "*".

[github-actions]

👋 Hey Friends, this issue has been automatically marked as stale because it has no recent activity. It will be closed if no further activity occurs. Please add the Status: Pinned label if you feel that this issue needs to remain open/active. Thank you for your contributions and help in keeping things tidy!

[hartez]

A default instance of IssueFilter has all properties set to null, which in the resulting graph query will compare all the fields to null. However, this means it looks for issues which have no milestone and no assignee. Since "*" includes all issues, I suggest that IssueFilter initializes Milestone and Assignee to "*".

As far as I can tell, * does not return any issue which doesn't have a value for the specified field. So null for Milestone doesn't match any issues with milestones assigned, and * doesn't match issues which don't have any milestones. So either way, issues are being excluded. It feels like there should be some way to get issues regardless of whether they have a milestone or assignee.