Why add force with vanish parameters?

[ljw20180420]

Even if a force does not have type, say Harmonic, it will be added to md.bond.Harmonic() with vanish parameters. Similar case happens for angles. Is this necessary? Does it harm the performance?

polychrom-hoomd/polychrom_hoomd/forces.py

Lines 168 to 169 in 27b983b

	else:
	harmonic_force.params[bond_type] = dict(k=0, r0=0)

polychrom-hoomd/polychrom_hoomd/forces.py

Lines 217 to 218 in 27b983b

	else:
	angular_force.params[angle_type] = dict(U=[0], tau=[0])