In SwWW8ImplReader::StopApo() the JoinNext() may delete the node that
pPaM points to.  It is probably a bad idea to use a non-correctable
SwPaM in an import filter; sadly this filter uses the core API directly,
let's use a SwUnoCrsr which should avoid the problem.

Change-Id: I120a481883b7ecbfa59cc998153fec0e6b9bafe5