FutureWarning: Comparison to `None` behaviour will change

[demisjohn]

Got this error upon simulating Cavity Modes:

pyfimm\__Device.py:376: FutureWarning: comparison to `None` will result in an elementwise object comparison in the future.
  if mode_vector == None:

Perhaps use np.all( x == None ) to handle element-wise comparison? Or maybe the variables being compared are already single-elements. (But future comparison will return an array instead of single value?)