No video getting generated (new question/problem to solve)

Hi,
I have a slight problem with the video output....

I have read the Issue #258 (wich has the same title as mine), but could not solve the problem. I get no Error message and no preview just two folders as output. They are in __Media\Designs__ and are called _raster_images_ and _svg_images_.

Here is my test code:
```python
from manimlib.imports import *

#Test von Code

class QuadratZuKreis(Scene):
def grundgerüst(self):
kreis = Circle()
quadrat = Square()
quadrat.flip(RIGHT)
quadrat.rotate(-3*TAU /8)
kreis.set_fill(PINK, opacity = 0.5)

self.play(ShowCreation(quadrat))
self.play(Transform(quadrat, kreis))
self.play(FadeOut(quadrat))
```
And a second one I copied just to make shure it is not the code, were the same is happening:

```python
from manimlib.imports import *

class Shapes(Scene):
def construct(self):
circle = Circle()
square = Square()
line=Line(np.array([3,0,0]),np.array([5,0,0]))
triangle=Polygon(np.array([0,0,0]),np.array([1,1,0]),np.array([1,-1,0]))

self.add(line)
self.play(ShowCreation(circle))
self.play(FadeOut(circle))
self.play(GrowFromCenter(square))
self.play(Transform(square,triangle))
```

With kind regards