i3bar Bugfix: don't show "EOF" status line error

Long description:

When the `status_command` sends EOF, it is terminated. Terminating this
process prints an error message to the status line (hence, a race
condition). This error message is always more useful than the former
"EOF" status line error because it shows the exit code.

To apply this patch, use:
curl http://cr.i3wm.org/patch/370/raw.patch | git am

@@ -288,8 +288,6 @@ static unsigned char *get_buffer(ev_io *watcher, int *ret_buffer_len) {

             /* end of file, kill the watcher */

             ELOG("stdin: received EOF\n");

             cleanup();

-            set_statusline_error("Received EOF from statusline process");

-            draw_bars(false);

             *ret_buffer_len = -1;

             return NULL;

         }