phase_crossover_frequencies generates errors with poles at origin #1105

^{Originally posted by alittlepinetree December 31, 2024}
When I used this function to calculate the phase crossover frequencies, it didn't work.
`import control
import matplotlib.pyplot as plt

G = control.tf([200.0], [1.0, 21.0, 20.0, 0.0])
x_omega, x_gain = control.phase_crossover_frequencies(G)
print(x_omega)`