Bug#1040484: Warning: global/dynamic var, ‘begin’ lacks a prefix

[AlMa]

Package: auctex
Version: 12.2-1

Reproduce:
1) temporarily remove ~/.emacs
2) start `emacs nonexistent_file.tex`, where nonexistent_file.tex 
shouldn't exist
3) Observe
/usr/share/emacs/site-lisp/auctex/preview.elc: Warning: global/dynamic var
    ‘begin’ lacks a prefix

in the buffer *Compile-Log*.

This shouldn't happen.