export: Fix empty realm_icons directory in single-user exports.
export: Fix empty realm_icons directory in single-user exports.

kou/zulip,eeshangarg/zulip,rht/zulip,eeshangarg/zulip,rht/zulip,rht/zulip,eeshangarg/zulip,andersk/zulip,eeshangarg/zulip,andersk/zulip,kou/zulip,kou/zulip,andersk/zulip,rht/zulip,zulip/zulip,eeshangarg/zulip,eeshangarg/zulip,kou/zulip,eeshangarg/zulip,andersk/zulip,zulip/zulip,rht/zulip,zulip/zulip,andersk/zulip,kou/zulip,andersk/zulip,andersk/zulip,zulip/zulip,rht/zulip,rht/zulip,zulip/zulip,zulip/zulip,kou/zulip,zulip/zulip,kou/zulip