small fix in single photon beamlet stf generator

Author: wahln

matRad/steering/matRad_PhotonStfGeneratorSingleBeamlet.m

@@ -53,7 +53,7 @@
                 checkBasic = isfield(machine,'meta') && isfield(machine,'data');
 
                 %check modality
-                checkModality = any(strcmp(matRad_PhotonStfGeneratorSingleBeamlet.possibleRadiationModes, machine.meta.radiationMode)) && any(strcmp(matRad_PhotonStfGeneratorIMRT.possibleRadiationModes, pln.radiationMode));
+                checkModality = any(strcmp(matRad_PhotonStfGeneratorSingleBeamlet.possibleRadiationModes, machine.meta.radiationMode)) && any(strcmp(atRad_PhotonStfGeneratorSingleBeamlet.possibleRadiationModes, pln.radiationMode));
 
                 %Sanity check compatibility
                 if checkModality