I checked again and without any other manipulation all icons are no present on the buttons.
Also the new feature allowing to create profiles before launching and connecting the indi-server to devices works very well.
In order to repeat, I just upgraded to Ubuntu-Mate 16.04 and installed kstars-bleedingedge and it is all OK.
Yes that may happen if you have more than one version installed, I had no problems either with the RPi or the 2 PC's I have installed.
It didn't ask me for dependencies, maybe because I had them already installed.
Anyway thanks for the warning, I should mention, first try the last post:
sudo apt-get install oxygen-icon-theme
that fixed the problem too and it's probably safer.