tdf#135018 sw_redlinehide: fix accept delete redline at start of body

There is no predecessor text node.

(regression from 34b32f56e7f76639ee3a31cfc230a3340acf635a)

Change-Id: I5f6a1a7a1a35a2a6e600166dc1afcf6c4bf9d389
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/101337
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@cib.de>
diff --git a/sw/source/core/txtnode/ndtxt.cxx b/sw/source/core/txtnode/ndtxt.cxx
index 1dd2139..57a605f 100644
--- a/sw/source/core/txtnode/ndtxt.cxx
+++ b/sw/source/core/txtnode/ndtxt.cxx
@@ -871,7 +871,10 @@ void CheckResetRedlineMergeFlag(SwTextNode & rNode, Recreate const eRecreateMerg
    if (eRecreateMerged != sw::Recreate::No)
    {
        SwTextNode * pMergeNode(&rNode);
        if (eRecreateMerged == sw::Recreate::Predecessor)
        if (eRecreateMerged == sw::Recreate::Predecessor
            // tdf#135018 check that there is a predecessor node, i.e. rNode
            // isn't the first node after the body start node
            && rNode.GetNodes()[rNode.GetIndex() - 1]->StartOfSectionIndex() != 0)
        {
            for (sal_uLong i = rNode.GetIndex() - 1; ; --i)
            {