Minor fix in Postfix Evaluation Exercise
Minor fix in Postfix Evaluation Exercise

RJFreund/OpenDSA,RJFreund/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,RJFreund/OpenDSA,RJFreund/OpenDSA,RJFreund/OpenDSA,RJFreund/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,hosamshahin/OpenDSA,RJFreund/OpenDSA,RJFreund/OpenDSA,hosamshahin/OpenDSA