narrow_banner: Refactor first_operand conditionals to use switch/case.
narrow_banner: Refactor first_operand conditionals to use switch/case.

zulip/zulip,rht/zulip,punchagan/zulip,andersk/zulip,punchagan/zulip,punchagan/zulip,eeshangarg/zulip,punchagan/zulip,andersk/zulip,andersk/zulip,rht/zulip,andersk/zulip,punchagan/zulip,rht/zulip,eeshangarg/zulip,hackerkid/zulip,hackerkid/zulip,hackerkid/zulip,kou/zulip,kou/zulip,kou/zulip,zulip/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,kou/zulip,hackerkid/zulip,rht/zulip,zulip/zulip,eeshangarg/zulip,zulip/zulip,kou/zulip,andersk/zulip,hackerkid/zulip,zulip/zulip,rht/zulip,hackerkid/zulip,punchagan/zulip,eeshangarg/zulip,zulip/zulip,eeshangarg/zulip,andersk/zulip,kou/zulip,rht/zulip,eeshangarg/zulip,punchagan/zulip,andersk/zulip,hackerkid/zulip,kou/zulip