Problem: ml_get error when scrolling after delete
Solution: mark topline to be validated in main_loop
if it is larger than current buffers line
count
reset_lnums() is called after e.g. TextChanged autocommands and it may
accidentally cause curwin->w_topline to become invalid, e.g. if the
autocommand has deleted some lines.
So verify that curwin->w_topline points to a valid line and if not, mark
the window to have w_topline recalculated in main_loop() in
update_topline() after reset_lnums() returns.
fixes: vim/vim#13568fixes: vim/vim#13578c4ffeddfe5
The error doesn't happen in Nvim because Nvim triggers TextChanged after
calling update_topline().
Co-authored-by: Christian Brabandt <cb@256bit.org>
