tdf#130960 compare documents does not work

regression from
    commit 0528012fd0dc4b93645ef7790b0db9d1cecbae66
    loplugin:constantparam

Change-Id: I7e6d366c60da95f7839755e4ce228cfeff7354af
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/89618
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
diff --git a/sw/source/core/doc/doccomp.cxx b/sw/source/core/doc/doccomp.cxx
index beaddb5..3e8fef2 100644
--- a/sw/source/core/doc/doccomp.cxx
+++ b/sw/source/core/doc/doccomp.cxx
@@ -149,8 +149,8 @@ public:
class CompareMainText : public CompareData
{
public:
    CompareMainText(SwDoc &rD)
        : CompareData(rD, false)
    CompareMainText(SwDoc &rD, bool bRecordDiff)
        : CompareData(rD, bRecordDiff)
    {
    }

@@ -1780,8 +1780,8 @@ namespace
    {
        Comparators aComparisons;
        //compare main text
        aComparisons.emplace_back(std::make_shared<CompareMainText>(rSrcDoc),
                                  std::make_shared<CompareMainText>(rDestDoc));
        aComparisons.emplace_back(std::make_shared<CompareMainText>(rSrcDoc, true),
                                  std::make_shared<CompareMainText>(rDestDoc, true));

        //if we have the same number of frames then try to compare within them
        const SwFrameFormats *pSrcFrameFormats = rSrcDoc.GetSpzFrameFormats();
@@ -2082,8 +2082,8 @@ long SwDoc::MergeDoc( const SwDoc& rDoc )
    rSrcDoc.getIDocumentRedlineAccess().SetRedlineFlags( RedlineFlags::ShowDelete );
    getIDocumentRedlineAccess().SetRedlineFlags( RedlineFlags::ShowDelete );

    CompareMainText aD0(rSrcDoc);
    CompareMainText aD1(*this);
    CompareMainText aD0(rSrcDoc, false);
    CompareMainText aD1(*this, false);
    aD1.CompareLines( aD0 );
    if( !aD1.HasDiffs( aD0 ) )
    {