Can not enable "Electrical Potential" for year != 2000

[Erik Johansson]

Appears one can not enable "Electrical Potential" for year != 2000. Tries to read file "userdata/c2g_1999.dat" etc.. The only existing one is "userdata/c2g_2000.dat".

Typical error message (stdout): CGMC: Reading file "userdata/g2c_2016.dat" Cannot load: userdata/g2c_2016.dat CGMC: Reading file "userdata/c2g_2016.dat" Cannot load: userdata/c2g_2016.dat ovt.object.ElectPot -> java.lang.Exception: CGMC not initialized