gbx: Protect against invalid short messages.



git-svn-id: http://streamboard.de.vu/svn/oscam/trunk@9537 4b0bc96b-bc66-0410-9d44-ebda105a78c1
gbx: Do not accept ECM with ID=0;



git-svn-id: http://streamboard.de.vu/svn/oscam/trunk@9538 4b0bc96b-bc66-0410-9d44-ebda105a78c1