Add coverage for update_existing_reaction().
Add coverage for update_existing_reaction().

andersk/zulip,jrowan/zulip,jackrzhang/zulip,synicalsyntax/zulip,Galexrt/zulip,brockwhittaker/zulip,rht/zulip,rht/zulip,vabs22/zulip,zulip/zulip,timabbott/zulip,vaidap/zulip,jackrzhang/zulip,jrowan/zulip,amanharitsh123/zulip,Galexrt/zulip,kou/zulip,zulip/zulip,shubhamdhama/zulip,brainwane/zulip,timabbott/zulip,Galexrt/zulip,zulip/zulip,verma-varsha/zulip,timabbott/zulip,showell/zulip,eeshangarg/zulip,tommyip/zulip,punchagan/zulip,rht/zulip,vaidap/zulip,mahim97/zulip,hackerkid/zulip,hackerkid/zulip,tommyip/zulip,timabbott/zulip,tommyip/zulip,brainwane/zulip,mahim97/zulip,brockwhittaker/zulip,vabs22/zulip,punchagan/zulip,tommyip/zulip,tommyip/zulip,brockwhittaker/zulip,hackerkid/zulip,jackrzhang/zulip,andersk/zulip,tommyip/zulip,dhcrzf/zulip,mahim97/zulip,dhcrzf/zulip,verma-varsha/zulip,jrowan/zulip,punchagan/zulip,eeshangarg/zulip,mahim97/zulip,rishig/zulip,synicalsyntax/zulip,brainwane/zulip,punchagan/zulip,shubhamdhama/zulip,brainwane/zulip,kou/zulip,rishig/zulip,jrowan/zulip,showell/zulip,rishig/zulip,rishig/zulip,brainwane/zulip,kou/zulip,brockwhittaker/zulip,amanharitsh123/zulip,dhcrzf/zulip,brockwhittaker/zulip,zulip/zulip,andersk/zulip,synicalsyntax/zulip,verma-varsha/zulip,verma-varsha/zulip,eeshangarg/zulip,shubhamdhama/zulip,shubhamdhama/zulip,dhcrzf/zulip,andersk/zulip,mahim97/zulip,zulip/zulip,jackrzhang/zulip,showell/zulip,showell/zulip,Galexrt/zulip,eeshangarg/zulip,timabbott/zulip,dhcrzf/zulip,hackerkid/zulip,punchagan/zulip,timabbott/zulip,Galexrt/zulip,synicalsyntax/zulip,hackerkid/zulip,rht/zulip,kou/zulip,hackerkid/zulip,shubhamdhama/zulip,synicalsyntax/zulip,andersk/zulip,amanharitsh123/zulip,punchagan/zulip,amanharitsh123/zulip,rishig/zulip,verma-varsha/zulip,vabs22/zulip,vabs22/zulip,shubhamdhama/zulip,zulip/zulip,jackrzhang/zulip,jackrzhang/zulip,brockwhittaker/zulip,Galexrt/zulip,showell/zulip,synicalsyntax/zulip,mahim97/zulip,vaidap/zulip,dhcrzf/zulip,rishig/zulip,eeshangarg/zulip,showell/zulip,vaidap/zulip,vabs22/zulip,vaidap/zulip,vaidap/zulip,andersk/zulip,showell/zulip,eeshangarg/zulip,dhcrzf/zulip,kou/zulip,amanharitsh123/zulip,amanharitsh123/zulip,jrowan/zulip,brainwane/zulip,zulip/zulip,rishig/zulip,kou/zulip,verma-varsha/zulip,brainwane/zulip,rht/zulip,eeshangarg/zulip,Galexrt/zulip,shubhamdhama/zulip,kou/zulip,tommyip/zulip,punchagan/zulip,vabs22/zulip,andersk/zulip,rht/zulip,jackrzhang/zulip,timabbott/zulip,jrowan/zulip,rht/zulip,synicalsyntax/zulip,hackerkid/zulip