Null array returned in TDIFlyGB with drop_points=0

[DrizzleatDusk]

Description

Calling TDIFlyGB to calculate the waveform in time domain with default drop_points=0 will return an array filled with 0.

Reason

The 360th line of TDIFly.py

res[:, -self.drop_points:] = 0. 

means

res[:, 0:] = 0. 

and thus causes all the items of the res equal to 0.

Is this an expected mechanism to force non-zero drop_points to be passed in?