add unhandled case in switch

Change-Id: I1e6c2263cb8e6b4d58a3f63ca129d4e9c403fce2
diff --git a/sc/source/filter/excel/xeextlst.cxx b/sc/source/filter/excel/xeextlst.cxx
index ebfe2cd..6982ec3 100644
--- a/sc/source/filter/excel/xeextlst.cxx
+++ b/sc/source/filter/excel/xeextlst.cxx
@@ -383,6 +383,7 @@ XclExpExtCalcPr::XclExpExtCalcPr( const XclExpRoot& rRoot, formula::FormulaGramm
        case formula::FormulaGrammar::CONV_XL_OOX:
        case formula::FormulaGrammar::CONV_LOTUS_A1:
        case formula::FormulaGrammar::CONV_LAST:
        case formula::FormulaGrammar::CONV_A1_XL_A1:
            maSyntax = OString("Unspecified");
            break;
    }