Fix handling of empty environment variables in PAL.
Fix handling of empty environment variables in PAL.

ruben-ayrapetyan/coreclr,poizan42/coreclr,YongseopKim/coreclr,wateret/coreclr,gkhanna79/coreclr,wateret/coreclr,ruben-ayrapetyan/coreclr,russellhadley/coreclr,YongseopKim/coreclr,alexperovich/coreclr,yizhang82/coreclr,gkhanna79/coreclr,JonHanna/coreclr,mmitche/coreclr,James-Ko/coreclr,cydhaselton/coreclr,hseok-oh/coreclr,JosephTremoulet/coreclr,russellhadley/coreclr,jamesqo/coreclr,cmckinsey/coreclr,botaberg/coreclr,krytarowski/coreclr,kyulee1/coreclr,gkhanna79/coreclr,jamesqo/coreclr,krk/coreclr,ragmani/coreclr,botaberg/coreclr,kyulee1/coreclr,pgavlin/coreclr,mmitche/coreclr,cydhaselton/coreclr,qiudesong/coreclr,cshung/coreclr,tijoytom/coreclr,cmckinsey/coreclr,gkhanna79/coreclr,sagood/coreclr,krytarowski/coreclr,YongseopKim/coreclr,yizhang82/coreclr,cydhaselton/coreclr,James-Ko/coreclr,mmitche/coreclr,AlexGhiondea/coreclr,botaberg/coreclr,JosephTremoulet/coreclr,pgavlin/coreclr,qiudesong/coreclr,qiudesong/coreclr,sagood/coreclr,wtgodbe/coreclr,yeaicc/coreclr,jamesqo/coreclr,sagood/coreclr,yizhang82/coreclr,wateret/coreclr,tijoytom/coreclr,wateret/coreclr,ragmani/coreclr,russellhadley/coreclr,JosephTremoulet/coreclr,JonHanna/coreclr,qiudesong/coreclr,kyulee1/coreclr,parjong/coreclr,krk/coreclr,hseok-oh/coreclr,James-Ko/coreclr,JosephTremoulet/coreclr,cydhaselton/coreclr,russellhadley/coreclr,hseok-oh/coreclr,ruben-ayrapetyan/coreclr,hseok-oh/coreclr,parjong/coreclr,mmitche/coreclr,wateret/coreclr,yizhang82/coreclr,russellhadley/coreclr,qiudesong/coreclr,ragmani/coreclr,AlexGhiondea/coreclr,qiudesong/coreclr,AlexGhiondea/coreclr,yeaicc/coreclr,pgavlin/coreclr,jamesqo/coreclr,yeaicc/coreclr,poizan42/coreclr,parjong/coreclr,krk/coreclr,dpodder/coreclr,krk/coreclr,wtgodbe/coreclr,parjong/coreclr,yeaicc/coreclr,parjong/coreclr,wtgodbe/coreclr,mskvortsov/coreclr,gkhanna79/coreclr,alexperovich/coreclr,kyulee1/coreclr,mskvortsov/coreclr,ruben-ayrapetyan/coreclr,botaberg/coreclr,ragmani/coreclr,kyulee1/coreclr,hseok-oh/coreclr,dpodder/coreclr,yeaicc/coreclr,cydhaselton/coreclr,ruben-ayrapetyan/coreclr,YongseopKim/coreclr,pgavlin/coreclr,JonHanna/coreclr,poizan42/coreclr,kyulee1/coreclr,tijoytom/coreclr,krk/coreclr,JosephTremoulet/coreclr,AlexGhiondea/coreclr,cmckinsey/coreclr,dpodder/coreclr,mskvortsov/coreclr,poizan42/coreclr,ruben-ayrapetyan/coreclr,yizhang82/coreclr,cmckinsey/coreclr,JonHanna/coreclr,James-Ko/coreclr,alexperovich/coreclr,parjong/coreclr,JonHanna/coreclr,ragmani/coreclr,russellhadley/coreclr,tijoytom/coreclr,mskvortsov/coreclr,alexperovich/coreclr,pgavlin/coreclr,cydhaselton/coreclr,mmitche/coreclr,krytarowski/coreclr,JosephTremoulet/coreclr,krytarowski/coreclr,cshung/coreclr,rartemev/coreclr,James-Ko/coreclr,cshung/coreclr,yizhang82/coreclr,botaberg/coreclr,gkhanna79/coreclr,cshung/coreclr,rartemev/coreclr,rartemev/coreclr,dpodder/coreclr,tijoytom/coreclr,yeaicc/coreclr,wtgodbe/coreclr,jamesqo/coreclr,dpodder/coreclr,alexperovich/coreclr,cshung/coreclr,tijoytom/coreclr,AlexGhiondea/coreclr,poizan42/coreclr,sagood/coreclr,cmckinsey/coreclr,alexperovich/coreclr,cmckinsey/coreclr,dpodder/coreclr,krytarowski/coreclr,rartemev/coreclr,mskvortsov/coreclr,mskvortsov/coreclr,poizan42/coreclr,YongseopKim/coreclr,mmitche/coreclr,krk/coreclr,James-Ko/coreclr,hseok-oh/coreclr,cmckinsey/coreclr,ragmani/coreclr,krytarowski/coreclr,wateret/coreclr,pgavlin/coreclr,wtgodbe/coreclr,sagood/coreclr,rartemev/coreclr,cshung/coreclr,rartemev/coreclr,YongseopKim/coreclr,JonHanna/coreclr,AlexGhiondea/coreclr,wtgodbe/coreclr,botaberg/coreclr,yeaicc/coreclr,sagood/coreclr,jamesqo/coreclr