Happens both in single player and multiplayer try and right click to use it and it crashes. Using most current version of GT++ and GT5u as well as forge for 1.7.10 if that helps.
crash-2017-01-08_20.06.49-client.txt

If you don't provided more details, I can't do anything to fix it.
Consider reading https://github.com/draknyte1/GTplusplus/wiki/Github-Issue-Format

will test on next release, thank you