Add math stuff into beamer section

Question

So here's a minimal code:

\documentclass[utf8]{beamer}
\usepackage{amsmath, amsthm, amssymb}
\begin{document}
    \section{$\frac{a}{b}$}
\end{document}

I tried the solution from this answer: Equations in section heading/title

But it doesn't work either:

\documentclass[utf8]{beamer}
\usepackage{amsmath, amsthm, amssymb}
\begin{document}
    \section{\texorpdfstring{$\frac{a}{b}$}}
\end{document}

This is the error message:

! Argument of \@firstoftwo has an extra }.
<inserted text>
                \par
l.6     \section{\texorpdfstring{$\frac{a}{b}$}}

Do you have an idea how I can add an little math environment into the sections?