export
of the latex fragment it would include the contents of
org-latex-packages-alist in the LaTex headers. Some
packages (namely
'fontspec,' used for xelatex) would lead to a failure to
create the
dvi file when the .tex file was compiled with the
necessary
'latex' command.
To
alleviate this problem I designed this wrapper function
which
sets org-latex-packages-alist to nil just before executing
the
org-latex-preview function.