make a copy of u-layer when iterating over it in fixCharge
make a copy of u-layer when iterating over it in fixCharge

in the loop we remove elements from the list. If we don't make a copy,
the loop goes wrong.

nickvandewiele/RMG-Py,chatelak/RMG-Py,nickvandewiele/RMG-Py,pierrelb/RMG-Py,chatelak/RMG-Py,nyee/RMG-Py,nyee/RMG-Py,pierrelb/RMG-Py