fix SwIndex assert on fdo66692-2.doc

Change-Id: Ic3330817809727bfa2293ba74dcd7f5a25683dae
(cherry picked from commit 2d2d5d1a)
Reviewed-on: https://gerrit.libreoffice.org/19378Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>

sw/source/filter/ww8/ww8par6.cxx

@@ -2513,6 +2513,21 @@ void SwWW8ImplReader::StopApo()
             if (rBrush.GetColor().GetColor() != COL_AUTO)
                 aBg = rBrush.GetColor();
 
+            if (m_pLastAnchorPos.get())
+            {
+                //If the last anchor pos is here, then clear the anchor pos.
+                //This "last anchor pos" is only used for fixing up the
+                //postions of things anchored to page breaks and here
+                //we are removing the last paragraph of a frame, so there
+                //cannot be a page break at this point so we can
+                //safely reset m_pLastAnchorPos to avoid any dangling
+                //SwIndex's pointing into the deleted paragraph
+                SwNodeIndex aLastAnchorPos(m_pLastAnchorPos->nNode);
+                SwNodeIndex aToBeJoined(aPref, 1);
+                if (aLastAnchorPos == aToBeJoined)
+                    m_pLastAnchorPos.reset();
+            }
+
             //Get rid of extra empty paragraph
             pNd->JoinNext();
         }