Fix propagation of lightbox body clicks closing compose box.
Fix propagation of lightbox body clicks closing compose box.

Like most event handlers where one successfully did something
specific, this event handler should stop event propagation.

Fixes #3885.

kou/zulip,timabbott/zulip,rht/zulip,christi3k/zulip,jainayush975/zulip,SmartPeople/zulip,j831/zulip,brainwane/zulip,eeshangarg/zulip,punchagan/zulip,verma-varsha/zulip,zulip/zulip,dattatreya303/zulip,dattatreya303/zulip,kou/zulip,showell/zulip,punchagan/zulip,verma-varsha/zulip,rishig/zulip,SmartPeople/zulip,kou/zulip,vaidap/zulip,punchagan/zulip,andersk/zulip,susansls/zulip,susansls/zulip,souravbadami/zulip,amanharitsh123/zulip,showell/zulip,timabbott/zulip,timabbott/zulip,dhcrzf/zulip,brockwhittaker/zulip,andersk/zulip,jphilipsen05/zulip,mahim97/zulip,andersk/zulip,aakash-cr7/zulip,jphilipsen05/zulip,JPJPJPOPOP/zulip,shubhamdhama/zulip,christi3k/zulip,ryanbackman/zulip,zulip/zulip,amanharitsh123/zulip,j831/zulip,dawran6/zulip,aakash-cr7/zulip,Galexrt/zulip,jrowan/zulip,Galexrt/zulip,souravbadami/zulip,aakash-cr7/zulip,dhcrzf/zulip,kou/zulip,vabs22/zulip,vaidap/zulip,synicalsyntax/zulip,jackrzhang/zulip,blaze225/zulip,samatdav/zulip,vaidap/zulip,brainwane/zulip,rishig/zulip,dattatreya303/zulip,dhcrzf/zulip,amanharitsh123/zulip,blaze225/zulip,ryanbackman/zulip,Galexrt/zulip,christi3k/zulip,SmartPeople/zulip,timabbott/zulip,hackerkid/zulip,jrowan/zulip,dawran6/zulip,eeshangarg/zulip,synicalsyntax/zulip,souravbadami/zulip,vabs22/zulip,JPJPJPOPOP/zulip,j831/zulip,PhilSk/zulip,hackerkid/zulip,dhcrzf/zulip,jackrzhang/zulip,mahim97/zulip,souravbadami/zulip,jphilipsen05/zulip,showell/zulip,tommyip/zulip,eeshangarg/zulip,Galexrt/zulip,jainayush975/zulip,eeshangarg/zulip,blaze225/zulip,vabs22/zulip,synicalsyntax/zulip,zulip/zulip,jainayush975/zulip,shubhamdhama/zulip,jackrzhang/zulip,samatdav/zulip,amanharitsh123/zulip,amanharitsh123/zulip,jainayush975/zulip,hackerkid/zulip,rishig/zulip,PhilSk/zulip,j831/zulip,brainwane/zulip,jphilipsen05/zulip,christi3k/zulip,punchagan/zulip,timabbott/zulip,kou/zulip,shubhamdhama/zulip,verma-varsha/zulip,synicalsyntax/zulip,dawran6/zulip,vaidap/zulip,JPJPJPOPOP/zulip,mahim97/zulip,susansls/zulip,JPJPJPOPOP/zulip,verma-varsha/zulip,tommyip/zulip,timabbott/zulip,rht/zulip,zulip/zulip,rishig/zulip,samatdav/zulip,vabs22/zulip,timabbott/zulip,jainayush975/zulip,showell/zulip,brainwane/zulip,ryanbackman/zulip,shubhamdhama/zulip,zulip/zulip,shubhamdhama/zulip,tommyip/zulip,brainwane/zulip,Galexrt/zulip,samatdav/zulip,dawran6/zulip,zulip/zulip,rishig/zulip,synicalsyntax/zulip,JPJPJPOPOP/zulip,JPJPJPOPOP/zulip,eeshangarg/zulip,punchagan/zulip,brockwhittaker/zulip,PhilSk/zulip,synicalsyntax/zulip,tommyip/zulip,rishig/zulip,tommyip/zulip,dattatreya303/zulip,blaze225/zulip,samatdav/zulip,hackerkid/zulip,showell/zulip,dhcrzf/zulip,brainwane/zulip,vaidap/zulip,verma-varsha/zulip,aakash-cr7/zulip,jphilipsen05/zulip,punchagan/zulip,tommyip/zulip,brockwhittaker/zulip,ryanbackman/zulip,vabs22/zulip,susansls/zulip,eeshangarg/zulip,rishig/zulip,SmartPeople/zulip,zulip/zulip,jainayush975/zulip,PhilSk/zulip,shubhamdhama/zulip,shubhamdhama/zulip,jackrzhang/zulip,Galexrt/zulip,dhcrzf/zulip,jackrzhang/zulip,vaidap/zulip,aakash-cr7/zulip,andersk/zulip,jphilipsen05/zulip,SmartPeople/zulip,tommyip/zulip,souravbadami/zulip,rht/zulip,hackerkid/zulip,dattatreya303/zulip,christi3k/zulip,jrowan/zulip,PhilSk/zulip,rht/zulip,andersk/zulip,mahim97/zulip,j831/zulip,andersk/zulip,blaze225/zulip,kou/zulip,susansls/zulip,PhilSk/zulip,kou/zulip,jrowan/zulip,jrowan/zulip,punchagan/zulip,dawran6/zulip,verma-varsha/zulip,vabs22/zulip,showell/zulip,samatdav/zulip,brainwane/zulip,ryanbackman/zulip,ryanbackman/zulip,jrowan/zulip,jackrzhang/zulip,dhcrzf/zulip,brockwhittaker/zulip,jackrzhang/zulip,rht/zulip,christi3k/zulip,rht/zulip,synicalsyntax/zulip,SmartPeople/zulip,dawran6/zulip,j831/zulip,souravbadami/zulip,Galexrt/zulip,brockwhittaker/zulip,andersk/zulip,hackerkid/zulip,brockwhittaker/zulip,mahim97/zulip,rht/zulip,hackerkid/zulip,susansls/zulip,aakash-cr7/zulip,showell/zulip,mahim97/zulip,dattatreya303/zulip,amanharitsh123/zulip,eeshangarg/zulip,blaze225/zulip