Category doesn't exist on New Topic

[RobD]

I just upgraded to the current git version of nodebb after I noticed that upgrading to 0.4.3. removed the Reply and New Topic buttons (no idea why that happened). The upgrade fixed that, but now when I try to create a new topic I just get the message "Category doesn't exist" when I click Submit (reply works though).
I'm running nodebb on Windows using mongodb. I had problems with categories before but managed to fix it manually, see https://community.nodebb.org/topic/1434/category-disappeared