unicode-math 包在由 XeLaTeX 编译时如果没有 \setmathfont 就会损坏

Question

昨天更新 TeXLive 2018 后，使用 XeLaTeX 编译文件时出现以下错误消息。

xelatex.exe> Runaway argument?
xelatex.exe> 76543210\q_stop newline - 'bold' (bx/n) with NFSS spec.: <->s*[0.9999\ETC.
xelatex.exe> ! File ended while scanning use of \__iow_wrap_end_chunk:w.
xelatex.exe> <inserted text> 
xelatex.exe>                 \par 

检查代码后，我发现这个错误发生在 TeXLive 和 MiKTeX 与 XeLaTeX 上。当我切换到 LuaLaTeX 或使用\setmathfont设置字体时，错误消失。以下是我电脑上的最小示例。有人知道是什么原因造成的吗？或者这是一个错误unicode-math？谢谢 : )

%% LyX 2.3.1-1 created this file.  For more info, see http://www.lyx.org/.
%% Do not edit unless you really know what you are doing.
\documentclass[11pt,twoside]{article}
\usepackage{fontspec}

\makeatletter
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Textclass specific LaTeX commands.
\newlength{\lyxlabelwidth}      % auxiliary length 

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% User specified LaTeX commands.
\usepackage{unicode-math}
%\setmathfont{texgyrepagella-math.otf}

\makeatother

\begin{document}
~
\end{document}