[Discussion] $QT_PLUGIN_PATH

I'm on NixOS. My host $QT_PLUGIN_PATH looks like this:

```
$ echo $QT_PLUGIN_PATH
/nix/store/fjkhr5kdp3lcb67jdwlh226mryahijls-plasma-workspace-6.5.5/lib/qt-6/plugins:/nix/store/110a5arwbz4fwhccvhac173cqf78c2qc-plasma5support-6.5.5/lib/qt-6/plugins:...
```

Distrobox forwards that env var to the containers, but those paths don't exist inside containers. This causes all Qt apps to crash, and to run them, I first need to `unset QT_PLUGIN_PATH`. Is there any reason Distrobox can't do this by default? (Looks like it would be done [here](https://github.com/89luca89/distrobox/blob/c6cc6a3d5bf541ebadd6fa64a0aaecb8292cea66/distrobox-enter#L442))

該 issue 指向 distrobox-enter 第 442 行，那里會處理環境變數。檢查 QT_PLUGIN_PATH 是如何被轉送的，以及在容器中取消設定該變數是否安全。透過修改指令碼，在進入容器前取消設定該變數來進行測試，並確認 Qt 應用程式不再崩潰。檢查是否還有其他類似的環境變數也需要進行相同處理。

由索引模型根據 Issue 內容生成。