tdf#105009 sw: fix a11y crash when removing drawing object

SwFrame::RemoveDrawObj() calls SwAnchoredObject::ChgAnchorFrame(0)
so the SwAnchoredDrawObj has no anchor frame later when
SwAccessibleMap::InvalidateCursorPosition() asks for the parent.

(regression from 76c549eb)

Change-Id: Id55cb5fc41a4e37e863498265d1565e1621d508e

sw/source/core/access/accfrmobj.cxx

@@ -379,10 +379,14 @@ const SwFrame* SwAccessibleChild::GetParent( const bool bInPagePreview ) const
             else
             {
                 // In any other case the parent is the root frm
-                if( bInPagePreview )
-                    pParent = pContact->GetAnchorFrame()->FindPageFrame();
-                else
-                    pParent = pContact->GetAnchorFrame()->getRootFrame();
+                SwFrame const*const pAnchor(pContact->GetAnchorFrame());
+                if (pAnchor) // null if object removed from layout
+                {
+                    if (bInPagePreview)
+                        pParent = pAnchor->FindPageFrame();
+                    else
+                        pParent = pAnchor->getRootFrame();
+                }
             }
         }
     }