test_messages: Expand tests for send_pm_if_empty_stream.
test_messages: Expand tests for send_pm_if_empty_stream.

This would have caught the last issue we had with this code path.

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