click_handlers: Refactor select_message_function.
click_handlers: Refactor select_message_function.

This uses the early-return pattern to make the main click handler for
opening the compose box more readable.

hackerkid/zulip,zulip/zulip,kou/zulip,synicalsyntax/zulip,showell/zulip,rht/zulip,brainwane/zulip,synicalsyntax/zulip,kou/zulip,kou/zulip,punchagan/zulip,andersk/zulip,brainwane/zulip,zulip/zulip,hackerkid/zulip,hackerkid/zulip,brainwane/zulip,zulip/zulip,timabbott/zulip,kou/zulip,brainwane/zulip,andersk/zulip,timabbott/zulip,punchagan/zulip,zulip/zulip,eeshangarg/zulip,hackerkid/zulip,timabbott/zulip,zulip/zulip,eeshangarg/zulip,punchagan/zulip,shubhamdhama/zulip,rht/zulip,synicalsyntax/zulip,showell/zulip,hackerkid/zulip,punchagan/zulip,synicalsyntax/zulip,rht/zulip,shubhamdhama/zulip,shubhamdhama/zulip,shubhamdhama/zulip,synicalsyntax/zulip,eeshangarg/zulip,showell/zulip,timabbott/zulip,andersk/zulip,showell/zulip,hackerkid/zulip,andersk/zulip,rht/zulip,rht/zulip,synicalsyntax/zulip,eeshangarg/zulip,showell/zulip,shubhamdhama/zulip,andersk/zulip,brainwane/zulip,hackerkid/zulip,eeshangarg/zulip,kou/zulip,andersk/zulip,showell/zulip,brainwane/zulip,timabbott/zulip,punchagan/zulip,timabbott/zulip,eeshangarg/zulip,timabbott/zulip,punchagan/zulip,brainwane/zulip,kou/zulip,zulip/zulip,zulip/zulip,rht/zulip,synicalsyntax/zulip,punchagan/zulip,shubhamdhama/zulip,rht/zulip,shubhamdhama/zulip,kou/zulip,eeshangarg/zulip,showell/zulip,andersk/zulip