[TOC] doesn't render /mathbb expressions

The line

`### Natürliche Zahlen $\mathbb{N}$`
shows up like this in the table of Content:
`Natürliche Zahlen N\mathbb{N}`

It might be nicer if it looks like this:
`Natürliche Zahlen N`
(without rendering as mathbb- N)

example code:

`[TOC]
# Mathematik
## Aufbau Zahlensystem
### Natürliche Zahlen $\mathbb{N}$
$\mathbb{N}=\{0,1,2,3,..\}$`