Throw an exception if soapEndPoint is empty. Refs #8719.
Log error instead of throwing exception. Refs #8719.

- As catalogPublish uses a custom dialog, throwing an exception causes Mantid to show a fatal error message.
No need to log the message. Refs #8719.

The ICAT server returns the correct error message when the session is not set.
Merge remote-tracking branch 'origin/feature/8719_icat_dialog_hang'