sw_redlinehide: old GCC needs a cast here

Change-Id: I45f340fff2d3285e1af6f6448c807d4997e5a42b
diff --git a/sw/source/core/text/txtfrm.cxx b/sw/source/core/text/txtfrm.cxx
index 39a0c82..52f5139 100644
--- a/sw/source/core/text/txtfrm.cxx
+++ b/sw/source/core/text/txtfrm.cxx
@@ -867,7 +867,7 @@ MapViewToModel(MergedPara const& rMerged, TextFrameIndex const i_nIndex)
    assert(nIndex == 0 && "view index out of bounds");
    return pExtent
        ? std::make_pair(pExtent->pNode, pExtent->nEnd) //1-past-the-end index
        : std::make_pair(rMerged.pFirstNode, 0);
        : std::make_pair(rMerged.pFirstNode, sal_Int32(0));
}

TextFrameIndex MapModelToView(MergedPara const& rMerged, SwTextNode const*const pNode, sal_Int32 const nIndex)