procid not being set for tcp RFC_5425 syslog message

Hello,

I've encountered a problem that the procid is not being set correctly -> procid seems to be either empty or "-" where long is expected.

```
messageSender = TcpSyslogMessageSender()
messageSender.syslogServerHostname = host
messageSender.defaultMessageHostname = host
messageSender.syslogServerPort = port
messageSender.defaultAppName = appName
messageSender.defaultFacility = Facility.LOCAL0
messageSender.messageFormat = MessageFormat.RFC_5425
messageSender.isSsl = true
messageSender.sslContext = sslContext
messageSender.defaultSeverity = Severity.INFORMATIONAL
messageSender.sendMessage(message)
messageSender.close()
```

Code used as above, everything else seems to be working correctly.

I'd be grateful for any help in this matter.