What steps will reproduce the problem?

Execute the following code. I use netrw help file as an example because it's a 
large file with many folds.

"-----BEGIN-----------------------------
edit $VIMRUNTIME/doc/pi_netrw.txt
" Change 'foldtext' to something different from default.
set foldtext=getline(v:foldstart)
set fdm=marker fdl=0
normal! ggzjzt
split
try
    throw 'oopsy-doopsy'
finally
endtry
"-----END-------------------------------


What is the expected output? What do you see instead?

The result is that some or all folded lines are displayed with the wrong value 
of 'foldtext' in both windows.
The display is corrected after Ctrl-L or after the cursor is moved.


What version of the product are you using? On what operating system?

Vim 7.3.829 from Cream project, Windows XP.


Please provide any additional information below.

This glitch affects the display of folded lines when an error occurs inside 
try/endtry and is not caught: folded lines are sometimes temporarily displayed 
with the wrong value of 'foldtext'. This is most noticeable when there are 
several windows with many closed folds.