Every callsite (bar one) calls setOwner and connectWithUntitledNumbers after construction,
so just pass them in the constructor.
And for that lone callsite we can just nullptr as an argument.
Change-Id: If838e068bb59a407225d853a0f67983be400f2f5
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/124426
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>