Show topics select in speed tagging interface

Apologies for the weird if/assignment. The speed tagging interface is
in need of some serious rework and this is intended as a quick/urgent
fix.
Merge pull request #1151 from alphagov/62001036-topics-when-speed-tagging

Show topics select in speed tagging interface

https://www.pivotaltracker.com/story/show/62001036