Description:
------------
detecting of callback is mistake in _php_bufferevent_errorcb.
see patch below.

Reproduce code:
---------------
*** libevent.c.old      2010-08-11 10:16:32.000000000 +0800
--- libevent.c  2010-08-11 10:17:04.000000000 +0800
*************** static void _php_bufferevent_errorcb(str
*** 297,303 ****
        php_bufferevent_t *bevent = (php_bufferevent_t *)arg;
        TSRMLS_FETCH_FROM_CTX(bevent ? bevent->thread_ctx : NULL);

!       if (!bevent || !bevent->base || !bevent->writecb) {
                return;
        }

--- 297,303 ----
        php_bufferevent_t *bevent = (php_bufferevent_t *)arg;
        TSRMLS_FETCH_FROM_CTX(bevent ? bevent->thread_ctx : NULL);

!       if (!bevent || !bevent->base || !bevent->errorcb) {
                return;
        }