Just slight improvement UI

All new users must make three posts to gain access to create new topics in all forums.
Therefore, the "Start new topic" blue button is almost always missing.

However, it should also be removed from the UI of thread https://waterpixels.net/forums/forum/33-critter-identification/

The button "Start new topic" is present in this thread (... but does not allow you to create a new topic and returns an error)