Follow-up (micro-?)optimisation

Change-Id: Ia49cb02b2374e1c284bb4dee77e333fe6c8839ce
diff --git a/sc/source/core/tool/compiler.cxx b/sc/source/core/tool/compiler.cxx
index 3730d24..ff1cbb1 100644
--- a/sc/source/core/tool/compiler.cxx
+++ b/sc/source/core/tool/compiler.cxx
@@ -1631,24 +1631,34 @@ void ScCompiler::SetRefConvention( FormulaGrammar::AddressConvention eConv )

const ScCompiler::Convention* ScCompiler::GetRefConvention( FormulaGrammar::AddressConvention eConv )
{
    static const ConventionOOO_A1 ConvOOO_A1;
    static const ConventionOOO_A1_ODF ConvOOO_A1_ODF;
    static const ConventionXL_A1 ConvXL_A1;
    static const ConventionXL_R1C1 ConvXL_R1C1;
    static const ConventionXL_OOX ConvXL_OOX;

    switch (eConv)
    {
        case FormulaGrammar::CONV_OOO:
        {
            static const ConventionOOO_A1 ConvOOO_A1;
            return &ConvOOO_A1;
        }
        case FormulaGrammar::CONV_ODF:
        {
            static const ConventionOOO_A1_ODF ConvOOO_A1_ODF;
            return &ConvOOO_A1_ODF;
        }
        case FormulaGrammar::CONV_XL_A1:
        {
            static const ConventionXL_A1 ConvXL_A1;
            return &ConvXL_A1;
        }
        case FormulaGrammar::CONV_XL_R1C1:
        {
            static const ConventionXL_R1C1 ConvXL_R1C1;
            return &ConvXL_R1C1;
        }
        case FormulaGrammar::CONV_XL_OOX:
        {
            static const ConventionXL_OOX ConvXL_OOX;
            return &ConvXL_OOX;
        }
        case FormulaGrammar::CONV_UNSPECIFIED:
        default:
            ;