Problem with ,,Missing begin{document}

After updating TexStudio to 3.0.1 I’ve faced with problem. When I try to compile file, that I have compiled many times earlier, I get error with text: "File `l3backend-pdfmode.def’ not found. begin{document}". What is wrong?
My code is:
documentclass[a4paper,12pt]{article}
begin{document}
text
end{document}

.log file content:

This is pdfTeX, Version 3.14159265-2.6-1.40.21 (TeX Live 2020/W32TeX)        (preloaded format=pdflatex 2020.5.21)  6 SEP 2020 19:42
entering extended mode
restricted write18 enabled.
%&-line parsing enabled.
**document.tex
(./document.tex
LaTeX2e <2020-02-02> patch level 5
L3 programming layer <2020-05-15>
(c:/texlive/2020/texmf-dist/tex/latex/base/article.cls
Document Class: article 2019/12/20 v1.4l Standard LaTeX document class
(c:/texlive/2020/texmf-dist/tex/latex/base/size12.clo
File: size12.clo 2019/12/20 v1.4l Standard LaTeX file (size option)
)
c@part=count167
c@section=count168
c@subsection=count169
c@subsubsection=count170
c@paragraph=count171
c@subparagraph=count172
c@figure=count173
c@table=count174
abovecaptionskip=skip47
belowcaptionskip=skip48
bibindent=dimen134
)

! LaTeX Error: File `l3backend-pdfmode.def' not found.

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

Enter file name: 
! Emergency stop.
<read *> 
     
l.2 begin{document}
                ^^M
*** (cannot read from terminal in nonstop modes)


Here is how much of TeX's memory you used:
 223 strings out of 480476
 2655 string characters out of 5903481
 239159 words of memory out of 5000000
 16342 multiletter control sequences out of 15000+600000
 532636 words of font info for 25 fonts, out of 8000000 for 9000
 1141 hyphenation exceptions out of 8191
 24i,0n,21p,141b,36s stack positions out of    5000i,500n,10000p,200000b,80000s
!  ==> Fatal error occurred, no output PDF file produced!