Can't install new extensions, buttons missing

I've just installed KNIME 3.3.1 on my Fedora 27 environment. Installation finished fine, but i've some problems with the options interfaces. 
For example, I tried to install a new extension and I've noticed that are missing the buttons at the right botton of the window.

As you can see from the picture above, I can't cofirm or cancel my action since buttons are missing.

Does anyone know how to fix this problem?

Thank you in advance

Best regards


Ok, I found a way to fix this problem (check original post). 
Basically what I 've done is edit the knime.ini file and add 


before the -vmargs line.

Restarting Knime, all buttons will be displayed.

I hope that this post will be useful for other users.