[BUGFIX] Correct condition when yaw_angles passed to TurboPark model (version 3)

[misi9170]

Equivalent bugfix to #808 for FLORIS v3. See #808 for details

The example code to run is slightly different (due to the change from 5d to 4d arrays in v4, #764):

import numpy as np
from floris.tools import FlorisInterface

fi = FlorisInterface("inputs/turbopark.yaml")
print(1)
fi.calculate_wake() # Raises warning
print(2)
fi.calculate_wake(yaw_angles=None) # Raises warning
print(3)
fi.calculate_wake(yaw_angles=np.zeros((1,1,3))) # Raises warning
print(4)
fi.calculate_wake(yaw_angles=np.array([[[20, 10, 0]]])) # Raises warning (due to 0)
print(5)
fi.calculate_wake(yaw_angles=np.array(([[[20, 20, 20]]]))) # No warning raised

Expected behavior, and what this PR implements, is that 1), 2), and 3) do not raise a warning, while 4) and 5) do.