Latex renders, but pdf generation(of all pages) fails

Example:

$C = \{\mathbf{u}_1,\mathbf{u}_2,\mathbf{u}_3, \mathbf{u}_4 \} $

Renders fine, but pdf generation fails because of the extra space at the end.

```
! LaTeX Error: \mathbf allowed only in math mode.

See the LaTeX manual or LaTeX Companion for explanation.
Type H for immediate help.
...

l.575 \$C = \{\mathbf
{u}\_1,\mathbf{u}\_2,\mathbf{u}\_3, \mathbf{u}\_4 \} \$
?
! Emergency stop.
```

Reproduce the failure with the provided LaTeX expression: it renders in the notebook but fails during PDF generation because of the trailing space. Start by tracing the notebook PDF export entry point; done means the example renders successfully in the generated PDF without breaking other pages.

Written by the indexing model from the issue text.