bug#38058: 12.2; Error triangle doesn't appear at once

[Per Starbäck]

Emacs  : GNU Emacs 26.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.26)
 of 2018-05-31
Package: 12.2

This happens to me all the time. I've excluded my own emacs
initializations in the example but then need to load tex-site
explicitly. I do:

$ emacs -q --no-site-file -l tex-site /tmp/foo.tex

where /tmp/foo.tex contains
------------------------------
\documentclass{article}

\begin{document}
\error
\end{document}
------------------------------

Then C-c C-c RET to run LaTeX which yields an error. Now the "error
triangle" in the toolbar doesn't appear (that is the "Next Error"
button). I expect it to appear.

If I switch buffer and then switch back again it will appear, for
example with M-x C-g to switch to the minibuffer and back.
Also just clicking with the mouse in the foo.tex buffer will make the
error triangle appear.

The emacs is self-compiled 26.1 running under GNU/Linux, Centos Centos 7.7.
It's running under X with Gnome. (This is not new behaviour in 12.2.
I recently updated to 12.2 partly to see if this was changed before
reporting it.)