notify_subscriptions_*: Fix use of leaked stream variable.
notify_subscriptions_*: Fix use of leaked stream variable.

While I believe this actually produced correct output since users are
always subscribed to streams within their realm, this code was
definitely wrong.

Discovered using the mypy type-checking tool.

dawran6/zulip,Diptanshu8/zulip,PhilSk/zulip,dhcrzf/zulip,samatdav/zulip,christi3k/zulip,ryansnowboarder/zulip,synicalsyntax/zulip,peguin40/zulip,susansls/zulip,tommyip/zulip,punchagan/zulip,grave-w-grave/zulip,rishig/zulip,hackerkid/zulip,umkay/zulip,peguin40/zulip,TigorC/zulip,zulip/zulip,vaidap/zulip,ahmadassaf/zulip,dwrpayne/zulip,kou/zulip,hackerkid/zulip,sup95/zulip,peiwei/zulip,souravbadami/zulip,jphilipsen05/zulip,eeshangarg/zulip,joyhchen/zulip,Juanvulcano/zulip,ryansnowboarder/zulip,grave-w-grave/zulip,grave-w-grave/zulip,amanharitsh123/zulip,Diptanshu8/zulip,PhilSk/zulip,krtkmj/zulip,christi3k/zulip,SmartPeople/zulip,rht/zulip,verma-varsha/zulip,Diptanshu8/zulip,peguin40/zulip,Jianchun1/zulip,SmartPeople/zulip,amanharitsh123/zulip,arpith/zulip,christi3k/zulip,ahmadassaf/zulip,amanharitsh123/zulip,umkay/zulip,mohsenSy/zulip,isht3/zulip,aakash-cr7/zulip,jphilipsen05/zulip,paxapy/zulip,samatdav/zulip,ryansnowboarder/zulip,arpith/zulip,dawran6/zulip,jrowan/zulip,dhcrzf/zulip,samatdav/zulip,TigorC/zulip,souravbadami/zulip,j831/zulip,rht/zulip,vikas-parashar/zulip,vaidap/zulip,reyha/zulip,rht/zulip,krtkmj/zulip,JPJPJPOPOP/zulip,paxapy/zulip,hackerkid/zulip,mohsenSy/zulip,isht3/zulip,dwrpayne/zulip,krtkmj/zulip,Jianchun1/zulip,KingxBanana/zulip,christi3k/zulip,jrowan/zulip,j831/zulip,jainayush975/zulip,dwrpayne/zulip,SmartPeople/zulip,Diptanshu8/zulip,souravbadami/zulip,jainayush975/zulip,ryanbackman/zulip,zulip/zulip,sup95/zulip,AZtheAsian/zulip,jrowan/zulip,joyhchen/zulip,mahim97/zulip,blaze225/zulip,zulip/zulip,cosmicAsymmetry/zulip,andersk/zulip,joyhchen/zulip,hackerkid/zulip,Juanvulcano/zulip,peguin40/zulip,souravbadami/zulip,rishig/zulip,blaze225/zulip,souravbadami/zulip,Galexrt/zulip,ryanbackman/zulip,timabbott/zulip,dhcrzf/zulip,ryansnowboarder/zulip,KingxBanana/zulip,eeshangarg/zulip,dawran6/zulip,brockwhittaker/zulip,dhcrzf/zulip,punchagan/zulip,arpith/zulip,jainayush975/zulip,zacps/zulip,jackrzhang/zulip,ryanbackman/zulip,jackrzhang/zulip,rht/zulip,umkay/zulip,peiwei/zulip,verma-varsha/zulip,dattatreya303/zulip,synicalsyntax/zulip,punchagan/zulip,isht3/zulip,vaidap/zulip,AZtheAsian/zulip,zulip/zulip,dattatreya303/zulip,mohsenSy/zulip,shubhamdhama/zulip,peiwei/zulip,jackrzhang/zulip,reyha/zulip,ryansnowboarder/zulip,grave-w-grave/zulip,cosmicAsymmetry/zulip,paxapy/zulip,zacps/zulip,sharmaeklavya2/zulip,sonali0901/zulip,amyliu345/zulip,ahmadassaf/zulip,peiwei/zulip,jackrzhang/zulip,susansls/zulip,samatdav/zulip,niftynei/zulip,sharmaeklavya2/zulip,amyliu345/zulip,KingxBanana/zulip,jphilipsen05/zulip,aakash-cr7/zulip,punchagan/zulip,Juanvulcano/zulip,SmartPeople/zulip,tommyip/zulip,timabbott/zulip,Vallher/zulip,showell/zulip,synicalsyntax/zulip,peguin40/zulip,Vallher/zulip,timabbott/zulip,vaidap/zulip,showell/zulip,sup95/zulip,Frouk/zulip,amanharitsh123/zulip,dwrpayne/zulip,dhcrzf/zulip,arpith/zulip,PhilSk/zulip,mahim97/zulip,TigorC/zulip,brainwane/zulip,joyhchen/zulip,dattatreya303/zulip,souravbadami/zulip,Jianchun1/zulip,cosmicAsymmetry/zulip,dawran6/zulip,jphilipsen05/zulip,dawran6/zulip,isht3/zulip,joyhchen/zulip,punchagan/zulip,timabbott/zulip,brockwhittaker/zulip,JPJPJPOPOP/zulip,JPJPJPOPOP/zulip,grave-w-grave/zulip,andersk/zulip,TigorC/zulip,mahim97/zulip,Frouk/zulip,ahmadassaf/zulip,sharmaeklavya2/zulip,andersk/zulip,jainayush975/zulip,jrowan/zulip,peiwei/zulip,blaze225/zulip,aakash-cr7/zulip,vikas-parashar/zulip,peguin40/zulip,shubhamdhama/zulip,ahmadassaf/zulip,jackrzhang/zulip,ryansnowboarder/zulip,showell/zulip,brockwhittaker/zulip,reyha/zulip,KingxBanana/zulip,zulip/zulip,shubhamdhama/zulip,hackerkid/zulip,dwrpayne/zulip,Vallher/zulip,amanharitsh123/zulip,dwrpayne/zulip,arpith/zulip,Vallher/zulip,synicalsyntax/zulip,mahim97/zulip,reyha/zulip,jackrzhang/zulip,brainwane/zulip,vabs22/zulip,eeshangarg/zulip,cosmicAsymmetry/zulip,krtkmj/zulip,calvinleenyc/zulip,brainwane/zulip,kou/zulip,showell/zulip,sup95/zulip,andersk/zulip,amyliu345/zulip,JPJPJPOPOP/zulip,verma-varsha/zulip,Frouk/zulip,Diptanshu8/zulip,j831/zulip,paxapy/zulip,tommyip/zulip,grave-w-grave/zulip,Jianchun1/zulip,calvinleenyc/zulip,kou/zulip,brainwane/zulip,zulip/zulip,kou/zulip,zulip/zulip,kou/zulip,showell/zulip,ahmadassaf/zulip,PhilSk/zulip,umkay/zulip,kou/zulip,paxapy/zulip,Frouk/zulip,dhcrzf/zulip,showell/zulip,umkay/zulip,shubhamdhama/zulip,susansls/zulip,j831/zulip,paxapy/zulip,jackrzhang/zulip,calvinleenyc/zulip,samatdav/zulip,rishig/zulip,ryanbackman/zulip,shubhamdhama/zulip,rishig/zulip,dhcrzf/zulip,christi3k/zulip,brockwhittaker/zulip,zacps/zulip,zacps/zulip,Vallher/zulip,j831/zulip,brockwhittaker/zulip,Diptanshu8/zulip,rht/zulip,aakash-cr7/zulip,susansls/zulip,blaze225/zulip,vabs22/zulip,verma-varsha/zulip,jrowan/zulip,SmartPeople/zulip,PhilSk/zulip,Frouk/zulip,ryanbackman/zulip,calvinleenyc/zulip,rishig/zulip,vaidap/zulip,zacps/zulip,Vallher/zulip,Galexrt/zulip,isht3/zulip,vaidap/zulip,umkay/zulip,sonali0901/zulip,Frouk/zulip,AZtheAsian/zulip,jainayush975/zulip,synicalsyntax/zulip,samatdav/zulip,amyliu345/zulip,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