xref / intra-xref detection is incorrect when the root ID is not a book or article

[ghost]

(this bug is one to test later on, I am not completely sure it is valid)

It seems we only detect xrefs as intra-xref when they point to another book or article. However, when you build an individual chapter, we don't detect that xrefs outside of that chapter need to be displayed as unclickable intra-xrefs.

[janajaeger]

@tomschr can you shed some light on this?

[tomschr]

Non-issue. The intra-xrefs detects the target inside another book, article, etc.