DashedVMobject not returning correct output

When trying to draw a dashed line with custom length (width), it returns the continous version of the line.

```python
projection_line = DashedVMobject(
Line(point_a, point_b).set_width(100).set_color(YELLOW)
)
```

Also tried:
```python
projection_line = DashedVMobject(
Line(point_a, point_b).set_width(100)
).set_color(YELLOW)
```

And:
```python
projection_line = DashedVMobject(
Line(point_a, point_b)
).set_color(YELLOW).set_width(100)
```

查看 manim/mobject/types/vectorized_mobject.py 中的 DashedVMobject 類。了解它如何建立虛線以及 set_width 與它如何互動。執行提供的程式碼片段來重現此問題，然後追蹤方法呼叫，看看在設定 width 時 dash 生成失敗的位置。

由索引模型根據 Issue 內容生成。