Use OUStringBuffer in ScConcat

Change-Id: Ic1ee6e1a1d13afd7d205cdfb9f76f5e29a176378
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/131298
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
diff --git a/sc/source/core/tool/interpr1.cxx b/sc/source/core/tool/interpr1.cxx
index db8b282..d799623 100644
--- a/sc/source/core/tool/interpr1.cxx
+++ b/sc/source/core/tool/interpr1.cxx
@@ -9752,16 +9752,20 @@ void ScInterpreter::ScRept()
void ScInterpreter::ScConcat()
{
    sal_uInt8 nParamCount = GetByte();
    OUString aRes;

    //reverse order of parameter stack to simplify processing
    ReverseStack(nParamCount);

    OUStringBuffer aRes;
    while( nParamCount-- > 0)
    {
        OUString aStr = GetString().getString();
        if (CheckStringResultLen(aRes, aStr.getLength()))
            aRes = aStr + aRes;
            aRes.append(aStr);
        else
            break;
    }
    PushString( aRes );
    PushString( aRes.makeStringAndClear() );
}

FormulaError ScInterpreter::GetErrorType()