"Emergency stop" in `_global_settings.tex`

In TexLive 2025 ran on Windows, I encountered "Emergency stop" in `_global_settings.tex`.

This is raised due to `input` before `documentclass`.

I suggest move the following snips to `main.tex` before `\input{_global_settings.tex}`.
```
\ifdefined\DoubleSided
  \documentclass[twoside,openright,a4paper]{nusthesis}
\else
  \documentclass[a4paper]{nusthesis}
\fi
```