sw: ww8: ~SwIndexReg assertion:

Remove pointless SwPosition that triggers the assertion when loading
bugdoc from fdo#39006 from wwExtraneousParas::delete_all_from_doc.
diff --git a/sw/source/filter/ww8/ww8par.cxx b/sw/source/filter/ww8/ww8par.cxx
index 99a2544d..5c74e18 100644
--- a/sw/source/filter/ww8/ww8par.cxx
+++ b/sw/source/filter/ww8/ww8par.cxx
@@ -4134,8 +4134,7 @@ void wwExtraneousParas::delete_all_from_doc()
    {
        SwTxtNode *pTxtNode = *aI;
        SwNodeIndex aIdx(*pTxtNode);
        SwPosition aPos(aIdx);
        SwPaM aTest(aPos);
        SwPaM aTest(aIdx);
        m_rDoc.DelFullPara(aTest);
    }
    m_aTxtNodes.clear();