tdf#126071: fix assertion with offline help viewer

See bt here:
https://bugs.documentfoundation.org/attachment.cgi?id=152373
+
https://bugs.documentfoundation.org/show_bug.cgi?id=126071#c1

Change-Id: I6b9dcd0771d2e6df0cd89b3b0243d0d8defba685
Reviewed-on: https://gerrit.libreoffice.org/74716
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Jenkins
diff --git a/sfx2/source/appl/newhelp.cxx b/sfx2/source/appl/newhelp.cxx
index 8f6ccd8..fc60111 100644
--- a/sfx2/source/appl/newhelp.cxx
+++ b/sfx2/source/appl/newhelp.cxx
@@ -207,7 +207,7 @@
        Boundary aBoundary = xBreak->getWordBoundary(
            rSearchString, nStartPos, aLocale, WordType::ANYWORD_IGNOREWHITESPACES, true );

        while ( aBoundary.startPos != aBoundary.endPos )
        while ( aBoundary.startPos < aBoundary.endPos )
        {
            nStartPos = aBoundary.endPos;
            OUString sSearchToken( rSearchString.copy(