tdf#94624 calculation of power operator fixed

cell values are added in parentheses to make sure negative values are handled
correctly

Change-Id: I7366493e3cd6c25607e311d4b610ef8aa704a8bb
Reviewed-on: https://gerrit.libreoffice.org/19821Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Oliver Specht <oliver.specht@cib.de>

sw/source/core/fields/cellfml.cxx

@@ -366,8 +366,10 @@ void SwTableFormula::_MakeFormula( const SwTable& rTable, OUString& rNewStr,
         // calculate the value of the box
         if ( pSttBox->getRowSpan() >= 1 )
         {
+            rNewStr += "(";
             rNewStr += pCalcPara->rCalc.GetStrResult(
                             pSttBox->GetValue( *pCalcPara ), false );
+            rNewStr += ")";
         }
     }
     else