* FIX: New general category changes preventing topic create
Follow up to: #18383
The logic in the previous commit was checking for null, but we are
seeding the SiteSetting.general_category_id with an id of -1 so we need
to check for a positive value as well as checking for null.
See: https://meta.discourse.org/t/240661
* Add js test for presence of category… dropdown option