Fix issue with latest nightly (see Microsoft/Typescript#4497)
Fix issue with latest nightly (see Microsoft/Typescript#4497)

jbrantly/ts-loader,bjfletcher/ts-loader,gsteacy/ts-loader,jbrantly/ts-loader,TypeStrong/ts-loader,jbrantly/ts-loader,jaysoo/ts-loader,MortenHoustonLudvigsen/ts-loader,jaysoo/ts-loader,MortenHoustonLudvigsen/ts-loader,use-strict/ts-loader,TypeStrong/ts-loader,use-strict/ts-loader,gsteacy/ts-loader,MortenHoustonLudvigsen/ts-loader,bjfletcher/ts-loader,gsteacy/ts-loader