Emittance Monitor fails with zero emittance distribution

[JPTS2]

To test emittance evolution in a lepton collider with quantum radiation, blow up is being observed starting with bunches either: (1) starting on (0, 0, 0, 0, 0, 0) or (2) on (tw.x[0], tw.px[0], tw.y[0], tw.py[0], tw.zeta[0], tw.delta[0])

In both of these cases, the beam should have zero emittance but fails in two different ways:

Issue (1):

import xtrack as xt
import xcoll as xc
import numpy as np

particles = xt.Particles(
    x               = np.zeros(int(1E5)),
    px              = np.zeros(int(1E5)),
    y               = np.zeros(int(1E5)),
    py              = np.zeros(int(1E5)),
    zeta            = np.zeros(int(1E5)),
    delta           = np.zeros(int(1E5)))

moni = xc.EmittanceMonitor()

moni.track(particles)
gemitt_I    = moni.gemitt_I

Returns:

UFuncTypeError: Cannot cast ufunc 'multiply' output from dtype('complex128') to dtype('float64') with casting rule 'same_kind'

Issue (2):

import xtrack as xt
import xcoll as xc
import numpy as np

particles = xt.Particles(
    x               = np.full(int(1E5), 1E-5),
    px              = np.full(int(1E5), -2E-5),
    y               = np.full(int(1E5), 4E-5),
    py              = np.full(int(1E5), 5E-5),
    zeta            = np.full(int(1E5), 1E-3),
    delta           = np.full(int(1E5), -2E-4))

moni = xc.EmittanceMonitor()

moni.track(particles)
gemitt_I    = moni.gemitt_I

Returns:

ValueError: Invalid n2

Both of these can be fixed, as in both cases the covariance matrix (or in the monitor covariance matrix dot S) will be numerically all zero.