Bug: Searching through sufficiently large $historywords causes seg fault

[Marlon Richert <marlon.richert@xxxxxxxxx>]

However, this does not happen when searching through a normal array of
the same size:

% tmp=( {1..99999} )
% : $tmp[(r)foo]
% print -S "$tmp"
% : $historywords[(r)foo]
zsh: segmentation fault