tdf#133641 sw: fix crash double-clicking CH_TXT_ATR_FORMELEMENT

Only search for separator if there is one.

(regression from 1c94842e053a20a739a181d38a35c324df3e62a7)

Change-Id: I6697faa7cb83cab48084f9710f8c5018b9e738e2
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/95905
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@cib.de>
diff --git a/sw/source/core/crsr/swcrsr.cxx b/sw/source/core/crsr/swcrsr.cxx
index 9a7c84a..9756c57 100644
--- a/sw/source/core/crsr/swcrsr.cxx
+++ b/sw/source/core/crsr/swcrsr.cxx
@@ -1422,7 +1422,8 @@
        // Should we select the whole fieldmark?
        const IDocumentMarkAccess* pMarksAccess = GetDoc()->getIDocumentMarkAccess( );
        sw::mark::IFieldmark const*const pMark(pMarksAccess->getFieldmarkFor(*GetPoint()));
        if ( pMark )
        if (pMark && (IDocumentMarkAccess::GetType(*pMark) == IDocumentMarkAccess::MarkType::TEXT_FIELDMARK
                      || IDocumentMarkAccess::GetType(*pMark) == IDocumentMarkAccess::MarkType::DATE_FIELDMARK))
        {
            *GetPoint() = sw::mark::FindFieldSep(*pMark);
            ++GetPoint()->nContent; // Don't select the separator