Null concept answers in HL7 messages cause HL7InQueue hangup

A concept answer with a null value will cause the HL7InQueue queue to hang on that message indefinitely. An example of this issue:

MSH|^~\\&|FORMENTRY|AMRS.ELD|HL7LISTENER|AMRS.ELD|20080630094800||ORU^R01|kgWdFt0SVwwClOfJm3pe|P|2.5|1||||||||15^AMRS.ELD.FORMID
PID|||3^^^^~d3811480^^^^||John3^Doe^||
PV1||O|1^Unknown||||1^Super User (admin)|||||||||||||||||||||||||||||||||||||20080208|||||||V
ORC|RE||||||||20080208000000|1^Super User
OBR|1|||1238^MEDICAL RECORD OBSERVATIONS^99DCT
OBX|1|CWE|5497^CD4, BY FACS^99DCT||^^99DCT|||||||||20080208

Note the ^^99DCT answer above.

The expected behavior when this is encountered is for the HL7 message to be thrown to the HL7InError table. There is a debate at this time about the technique we should use to process the other observations while flagging this one for error resolution.