Refs #9349 - Move monitor det ID check to validator.

Code/Mantid/Framework/Algorithms/src/CalculateTransmission.cpp

@@ -44,7 +44,7 @@ void CalculateTransmission::init()
   auto zeroOrMore = boost::make_shared<BoundedValidator<int> >();
   zeroOrMore->setLower(0);
   // The defaults here are the correct detector numbers for LOQ
-  declareProperty("IncidentBeamMonitor",EMPTY_INT(),"The UDET of the incident beam monitor");
+  declareProperty("IncidentBeamMonitor",EMPTY_INT(),zeroOrMore,"The UDET of the incident beam monitor");
   declareProperty("TransmissionMonitor",3,zeroOrMore,"The UDET of the transmission monitor");
 
   declareProperty(new ArrayProperty<double>("RebinParams"),
@@ -75,11 +75,6 @@ void CalculateTransmission::exec()
   int beamMonitorID = getProperty("IncidentBeamMonitor");
   bool normaliseToMonitor = true;
   if ( isEmpty(beamMonitorID) ) normaliseToMonitor = false;
-  else if (beamMonitorID<0)
-  {
-    g_log.error("The beam monitor UDET should be greater or equal to zero");
-    throw std::invalid_argument("The beam monitor UDET should be greater or equal to zero");
-  }
 
   // Check that the two input workspaces are from the same instrument
   if ( sampleWS->getInstrument()->getName() != directWS->getInstrument()->getName() )