fdo#52013: Writer will crash when the undo-redoing if it contains dummy text

this fixes a regression introduced at 9c0ca924
by making assure that destination history has enough capacity

Change-Id: I3f608f7ab4a2617b695a5441d41553049cff333b

sw/source/core/inc/rolbck.hxx

@@ -399,6 +399,8 @@ public:
     {
         SwpHstry::iterator itSourceBegin = pIns->m_SwpHstry.begin() + nStart;
         SwpHstry::iterator itSourceEnd = pIns->m_SwpHstry.end();
+        if (itSourceBegin == itSourceEnd) return;
+        m_SwpHstry.reserve(nPos + static_cast<size_t>(itSourceEnd - itSourceBegin));
         std::copy( itSourceBegin, itSourceEnd, m_SwpHstry.begin() + nPos );
         pIns->m_SwpHstry.erase( itSourceBegin, itSourceEnd );
     }