Example Scene OpeningManimExample throws an out of range error since submobjects is empty.

I have just downloaded and installed Manim exactly as described in the instructions. I have MikTex and Ffmpeg etc installed too. I can run the SquaresToCircles example but this example fails.

```
File "D:\Development\Manim\manimlib\extract_scene.py", line 155, in main
scene = SceneClass(**scene_kwargs)
File "D:\Development\Manim\manimlib\scene\scene.py", line 75, in __init__
self.construct()
File "example_scenes.py", line 20, in construct
title = TextMobject("This is some \\LaTeX")
File "D:\Development\Manim\manimlib\mobject\svg\tex_mobject.py", line 150, in __init__
self.break_up_by_substrings()
File "D:\Development\Manim\manimlib\mobject\svg\tex_mobject.py", line 190, in break_up_by_substrings
sub_tex_mob.move_to(self.submobjects[last_submob_index], RIGHT)
IndexError: list index out of range
```

此錯誤發生在 tex_mobject.py 的第190行，當 submobjects 為空時。先檢查 example_scenes.py 中的 OpeningManimExample，以查看 TextMobject 的呼叫方式。查看 tex_mobject.py 中的 break_up_by_substrings 方法，釐清為何 submobjects 可能為空以及如何處理該情況。執行示例場景來重現此錯誤並驗證修復。

由索引模型根據 Issue 內容生成。