fix VShowPassingFlash index out of bounds issue

[germanzhu]

Motivation

Animation VShowPassingFlash often encounters an IndexError: index 0 is out of bounds for axis 0 with size 0.
for example:

from manimlib import *


class Video(Scene):
    
    def construct(self):
        s = TexText(r"A",template="tex")
        self.play(ShowCreation(s))
        self.play(VShowPassingFlash(s))

The error message is as follows:
File "test.py", line 9, in construct
self.play(VShowPassingFlash(s))
File "manimlib/scene/scene.py", line 405, in wrapper
func(self, *args, **kwargs)
File "manimlib/scene/scene.py", line 661, in play
self.begin_animations(animations)
File "manimlib/scene/scene.py", line 616, in begin_animations
animation.begin()
File "site-packages/manimlib/animation/indication.py", line 227, in begin
super().begin()
File "manimlib/animation/animation.py", line 79, in begin
self.interpolate(0)
File "manimlib/animation/animation.py", line 143, in interpolate
self.interpolate_mobject(alpha)
File "manimlib/animation/animation.py", line 155, in interpolate_mobject
self.interpolate_submobject(*mobs, sub_alpha)
File "manimlib/animation/indication.py", line 247, in interpolate_submobject
submobject.set_stroke(width=widths * gaussian)
File "manimlib/mobject/types/vectorized_mobject.py", line 207, in set_stroke
data['stroke_width'][:, 0] = resize_with_interpolation(
File "manimlib/utils/iterables.py", line 109, in resize_with_interpolation
return np.array([
File "manimlib/utils/iterables.py", line 110, in
(1 - a) * nparray[lh] + a * nparray[rh]
IndexError: index 0 is out of bounds for axis 0 with size 0

Proposed changes

• indication.py

Test

Code:

Result: