message: Fix memory error about hcc->client.
diff: @@ -836,15 +836,22 @@ static void http2_client_onConnect(swClient *cli)
  static void http2_client_onClose(swClient *cli)
  {
  zval *zobject = cli->object;
  + http2_client_property *hcc = swoole_get_property(zobject, HTTP2_CLIENT_CORO_PROPERTY);
  +
  zend_update_property_bool(swoole_http2_client_coro_class_entry_ptr, zobject, ZEND_STRL("connected"), 0 TSRMLS_CC);
  php_swoole_client_free(zobject, cli TSRMLS_CC);
  - http2_client_property *hcc = swoole_get_property(zobject,HTTP2_CLIENT_CORO_PROPERTY);
  - if (!hcc || hcc->iowait == 0) // when destruct hcc is null
  + if (!hcc)
  + {
  + return;
  + }
  + hcc->client = NULL;
  + if (hcc->iowait == 0)
  {
  return;
  }
  +
  hcc->cid = 0;
  hcc->iowait = 0;
  zval *result;
  @@ -867,12 +874,17 @@ static void http2_client_onError(swClient *cli)
  http2_client_property *hcc = swoole_get_property(zobject, HTTP2_CLIENT_CORO_PROPERTY);
  php_swoole_client_free(zobject, cli TSRMLS_CC);
  - hcc->client = NULL;
  - if (!hcc || hcc->iowait == 0)
  + if (!hcc)
  + {
  + return;
  + }
  + hcc->client = NULL;
  + if (hcc->iowait == 0)
  {
  return;
  }
  +
  hcc->cid = 0;
  hcc->iowait = 0;
  php_context *context = swoole_get_property(zobject, HTTP2_CLIENT_CORO_CONTEXT);
  