Fix a panic in the fluentd log driver when the collector address uses TLS, cannot be connected to, and fluentd-async is enabled. A failed tls.DialWithDialer returns a nil *tls.Conn, which connect() assigned to the net.Conn field. The field then held a non-nil interface wrapping a nil pointer, passed the nil check in close(), and crashed the daemon with a nil pointer dereference in tls.(*Conn).Close. full diff: https://github.com/fluent/fluent-logger-golang/compare/v1.10.1...v1.10.2 Signed-off-by: Takumi Akasaka <takumiakasaka1231@gmail.com>