arrow cannot be deleted in profil zone

Hello,

I had decided to work with slides of different levels, levels 1 and 2.  At the beginning an arrow appeared in the profil zone next to a bullet (level 1), indicating bullets of lower level (level 2).  You only had to click on the arrow to expand the level and so I could see the other bullets.

After that I decided to modify levels for some screens. 

Now I meet a problem.  I put level 1 to all the 5 slides.  There is no level 2 anymore.  Only these 5 slides can be seen in the profil zone.  That is well what I want.  The other slides are hidden.  The problem is that an arrow is always visible next to a bullet amongst the 5.  When you click on the arrow nothing happens.  I would like to delete it but it is not possible.  I don't see what could be done in "slides properties".  I have copied/pasted the slide itself but without any positive result.

Could you help me to solve that ?  If needed I can post you the zipped version of my presentation.

Thank you in advance.

Etienne