Potential PDF handling problem in pdf_include_page

[pkgw]

As revealed in crlf0710/tectonic#195. Potentially fixed with an analogy to crlf0710/tectonic#227? Minimal reproducer in the oxidized version seems to be:

\documentclass{article}
\usepackage{amsmath}
\usepackage{amssymb}

\begin{document}
$\widetilde{\mathbb{P}_{x}}$
\end{document}

Would be good to devise a case in the test suite for this.

CC @crlf0710 @burrbull @Mrmaxmeier

[burrbull]

This 2 issues are not related to each other.

[burrbull]

The issue with '\widetilde` was fixed somewhere in https://github.com/crlf0710/tectonic/compare/test_agl...crlf0710:test_agl2 and I can't determine the cause more precisely.

Tectonic master branch don't have problem that was fixed in https://github.com/crlf0710/tectonic/pull/227 due to this NULL assigning https://github.com/tectonic-typesetting/tectonic/blob/2210ff2214d25835064c042d90a84fd3ced8eed4/tectonic/dpx-epdf.c#L414