bug: double headed arrows leads to perpetual loading animation

[bfeitknecht]

The following snippet made with the online tikz-cd editor, quiver doesn't load at all, either the snippet doesn't render and just loads or displays a small icon (presumably some error indicator)

```tikz
\usepackage{tikzcd}
\begin{document}
\begin{tikzcd}
	\bullet & \bullet
	\arrow[tail reversed, from=1-1, to=1-2]
\end{tikzcd}
\end{document}
```

What worked for me was to "simulate" a double arrow by putting two arrows on top of each other.

```tikz
\usepackage{tikzcd}
\begin{document}
\begin{tikzcd}
	\bullet & \bullet
	\arrow[from=1-1, to=1-2]
	\arrow[from=1-2, to=1-1]
\end{tikzcd}
\end{document}
```