Last update breaks building my document

Fedora 34 Silverblue, Wayland.

I have a fairly standard document in Russian which I compile with XeLaTeX, nothing unusual. After the last update I'm getting these weird errors:


The first three line numbers don't change even when removing lines above them.

Here's the start of the document:

```
\documentclass[a4paper,12pt]{article}
\usepackage{fontspec}
\usepackage{polyglossia}
\usepackage{microtype}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsthm}
\usepackage{parskip}
\usepackage[nottoc]{tocbibind}
\usepackage{setspace}

\setmainlanguage{russian}
\setmainfont[Ligatures=TeX]{Liberation Serif}

\onehalfspacing
\frenchspacing

\begin{document}
```

Downgrading to before last Flathub commit fixed the issue.

Reproduce the failure with the provided Russian XeLaTeX preamble on Fedora 34 Silverblue, then compare the current Flathub build with the version before the last Flathub commit. Done means the supplied document builds successfully in the current Setzer package without the reported errors.

Written by the indexing model from the issue text.