Paths were checked for being at least 3 characters in length
before being added to FS_CATEGORY_OTHER.
It looks like this was originally done to prevent the preferences
attempting to add "//" paths which is now handled by `BLI_path_is_rel`.
As it happens the old logic prior to [0] was incorrect and asserted
if textures was set to "//textures" for example.
Now only check the path isn't empty.
[0]: 968f156fae
fbcdb748cd