committed to tl, r42797. thanks.

MWE

\documentclass[11pt]{article}%
\usepackage{amsmath,mathtools}
\usepackage{hyperref}
\begin{document}

\begin{align}
a &= b
\end{align}

\begin{equation}
a=b
\end{equation}

\end{document}

Compiled with

make4ht foo.tex 'htm,0,pic-align'

gives error

(/usr/local/texlive/2016/texmf-dist/tex/latex/graphics-cfg/graphics.cfg)))
Runaway argument?
\:tempc \choose:begin {\let \choose:begin \@firstoftwo \ifx \EndPicture \ETC.
! Paragraph ended before \:tempc was complete.
<to be read again>
\par

Please see

http://tex.stackexchange.com/questions/345689/paragraph-ended-before-tempc-was-complete-tex4ht-error/345706?noredirect=1#comment848208_345706

Michal was kind enough to look at it and provided a fix to use.

Adding this entry in database to keep track of this issue. Tex live 2016