tdf#104181 related: don't throw on this document

Change-Id: I53abf3267e1a75e944de82222c6ea80a72de0e7e
Reviewed-on: https://gerrit.libreoffice.org/33245Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
Tested-by: Mike Kaganski <mike.kaganski@collabora.com>

sw/source/core/layout/flowfrm.cxx

@@ -1800,6 +1800,9 @@ bool SwFlowFrame::MoveFwd( bool bMakePage, bool bPageBreak, bool bMoveAlways )
 {
 //!!!!MoveFootnoteCntFwd might need to be updated as well.
     SwFootnoteBossFrame *pOldBoss = m_rThis.FindFootnoteBossFrame();
+    assert(pOldBoss);
+    if (!pOldBoss)
+        return false;
     if (m_rThis.IsInFootnote())
     {
         if (!m_rThis.IsContentFrame())