How do I avoid my ~/.kde/tmp-sda2-enc/.kio_thumbnails* using all my free space

[user1]

> If it isn't important to you that those thumbnails are stored, you could
> simply make the directory read-only. The alternatives would be quota or
> a separate "thumbnail partition", I guess.

I have removed all the aprox 10 gb thumbnails in 
/home/user1/.kde/tmp-sda2-enc/

I have now a lot of empty directories in 
/home/username/.kde/tmp-sda2-enc/, but how do I remove those empty 
directories.

I have even tried following command
rmdir --ignore-fail-on-non-empty /home/username/.kde/tmp-sda2-enc/* but 
the empty directories will still not go away.