While looking around issues related to the recent 16.10.x versions, I noticed a bunch of them have no Component hence do not show up in several queries.
E.g. the Total issues link from 16.10.0 dashboard counts 65 issues Loading..., but replacing component != "Development Issues only" with component is EMPTY in the query reveals three more issues: Loading...
Is that on purpose? IMHO at least XWIKI-22627 is worth being mentioned.
In sounds wrong to me too. While it can happen when the issue is created and the reported does not have any idea where the problem is, it should definitely be set when fixed.
In our insternal Jira instance we have a couple of dedicated filters, like “Issues with no assignee” or “Issues with no release version” for similar reasons