bug#39097: 12.2.0; Preview gets lost and doesn't find the LaTeX source file

[Giacomo Boffi]

Dear Maintainer,

I have the file 'check.tex'

====================
\documentclass{article}
\begin{document}
\[ a=4 \]
\end{document}
====================

that I edit in Emacs, I have compiled it using pdflatex and everything
is fine - next from the Preview menu I select
"generate previews for document" and I get an error message


====================
error in process sentinel: LaTeX found no preview images
====================

and the '* .../check output *' buffer contains

====================
Running `Preview-LaTeX' on `check' with ``pdflatex  -file-line-error  
--synctex=1 
"\nonstopmode\nofiles\PassOptionsToPackage{active,tightpage,auctex}{preview}\AtBeginDocument{\ifx\ifPreview\undefined\RequirePackage[displaymath,floats,graphics,textmath,sections,footnotes]{preview}[2004/11/05]\fi}"
 "\input" "{\detokenize{" check.tex "}}"''
This is pdfTeX, Version 3.14159265-2.6-1.40.20 (TeX Live 2019/Debian) 
(preloaded format=pdflatex)
 restricted \write18 enabled.
entering extended mode
LaTeX2e <2019-10-01> patch level 3

No auxiliary output files.


! LaTeX Error: File ` check.tex ' not found.

Type X to quit or <RETURN> to proceed,
or enter new name. (Default extension: tex )

Enter file name: 
! Emergency stop.
<read *> 
         
<*> ...1/05]\fi} \input {\detokenize{ check.tex }}
                                                  ^^M
!  ==> Fatal error occurred, no output PDF file produced!
Transcript written on texput.log.

TeX Output exited as expected with code 1 at Sun Jan 12 00:09:52
LaTeX: LaTeX found no preview images
====================

Thank you in advance for your help
gb

==================================================================
Emacs  : GNU Emacs 26.3 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.11)
 of 2019-09-22, modified by Debian
Package: 12.2.0

current state:
==============
(setq
 AUCTeX-date "2019-10-31"
 window-system 'x
 LaTeX-version "2e"
 TeX-style-path '("~/.emacs.d/auctex" 
"/home/boffi/.emacs.d/elpa/auctex-12.1.2/style" 
"/home/boffi/.emacs.d/auctex/auto"
                  "/home/boffi/.emacs.d/auctex/style" "auto" "style")
 TeX-auto-save t
 TeX-parse-self t
 TeX-master t
 TeX-command-list '(("TeX" "%(PDF)%(tex) %(file-line-error) %`%(extraopts) 
%S%(PDFout)%(mode)%' %t" TeX-run-TeX nil
                     (plain-tex-mode ams-tex-mode texinfo-mode) :help "Run 
plain TeX")
                    ("LaTeX" "%`%l%(mode)%' %T" TeX-run-TeX nil (latex-mode 
doctex-mode) :help "Run LaTeX")
                    ("Makeinfo" "makeinfo %(extraopts) %t" TeX-run-compile nil 
(texinfo-mode) :help
                     "Run Makeinfo with Info output")
                    ("Makeinfo HTML" "makeinfo %(extraopts) --html %t" 
TeX-run-compile nil (texinfo-mode) :help
                     "Run Makeinfo with HTML output")
                    ("AmSTeX" "amstex %(PDFout) %`%(extraopts) %S%(mode)%' %t" 
TeX-run-TeX nil (ams-tex-mode) :help
                     "Run AMSTeX")
                    ("ConTeXt" "%(cntxcom) --once --texutil %(extraopts) 
%(execopts)%t" TeX-run-TeX nil (context-mode)
                     :help "Run ConTeXt once")
                    ("ConTeXt Full" "%(cntxcom) %(extraopts) %(execopts)%t" 
TeX-run-TeX nil (context-mode) :help
                     "Run ConTeXt until completion")
                    ("BibTeX" "%(bibtex) %s" TeX-run-BibTeX nil t :help "Run 
BibTeX")
                    ("Biber" "biber %s" TeX-run-Biber nil t :help "Run Biber")
                    ("View" "%V" TeX-run-discard-or-function t t :help "Run 
Viewer")
                    ("Print" "%p" TeX-run-command t t :help "Print the file")
                    ("Queue" "%q" TeX-run-background nil t :help "View the 
printer queue" :visible TeX-queue-command)
                    ("File" "%(o?)dvips %d -o %f " TeX-run-dvips t t :help 
"Generate PostScript file")
                    ("Dvips" "%(o?)dvips %d -o %f " TeX-run-dvips nil t :help 
"Convert DVI file to PostScript")
                    ("Dvipdfmx" "dvipdfmx %d" TeX-run-dvipdfmx nil t :help 
"Convert DVI file to PDF with dvipdfmx")
                    ("Ps2pdf" "ps2pdf %f" TeX-run-ps2pdf nil t :help "Convert 
PostScript file to PDF")
                    ("Glossaries" "makeglossaries %s" TeX-run-command nil t 
:help
                     "Run makeglossaries to create glossary file")
                    ("Index" "%(makeindex) %s" TeX-run-index nil t :help "Run 
makeindex to create index file")
                    ("upMendex" "upmendex %s" TeX-run-index t t :help "Run 
upmendex to create index file")
                    ("Xindy" "texindy %s" TeX-run-command nil t :help "Run 
xindy to create index file")
                    ("Check" "lacheck %s" TeX-run-compile nil (latex-mode) 
:help "Check LaTeX file for correctness")
                    ("ChkTeX" "chktex -v6 %s" TeX-run-compile nil (latex-mode) 
:help
                     "Check LaTeX file for common mistakes")
                    ("Spell" "(TeX-ispell-document \"\")" TeX-run-function nil 
t :help "Spell-check the document")
                    ("Clean" "TeX-clean" TeX-run-function nil t :help "Delete 
generated intermediate files")
                    ("Clean All" "(TeX-clean t)" TeX-run-function nil t :help
                     "Delete generated intermediate and output files")
                    ("Other" "" TeX-run-command t t :help "Run an arbitrary 
command"))
 )