Copy was using the real line length which after resize can be larger than the screen width. When built with -DDEBUG, this made the grid bounds checking code kill the server. Restrict copying to the actual width.
Copy was using the real line length which after resize can be larger than the
screen width. When built with -DDEBUG, this made the grid bounds checking code
kill the server. Restrict copying to the actual width.

From Kalle Olavi Niemitalo, thanks.

klaxalk/tmux,klaxalk/tmux,klaxalk/tmux,klaxalk/tmux,klaxalk/tmux