A JavaScript error occured in the main process while trying to run GeoGebra 6 Portable
This fix worked for me :
sudo touch /usr/share/geogebra-classic/resources/app/ggb-config.js
for the same error with geogebra-classic_6.0.400.0-201711172340_amd64.deb version, found here.
source : https://help.geogebra.org/topic/geogebra-classic_6-0-400-0-201711172340_amd64-deb-is-broken