Error message for empty CF node

Until the problem is fixed in the Gaudi scheduler (see gaudi/Gaudi#135 (closed)), throw an error if a problematic empty sequence is found in the HLT menu.

Trigger/TriggerCommon/TriggerMenuMT/python/HLTMenuConfig/Menu/CFValidation.py

@@ -20,6 +20,11 @@ def findViewAlgs( inputNodes, viewNodes ):
         # If node is a sequence, explore further
         if isSequence( node ):
 
+            # Empty nodes can cause Gaudi scheduler bug https://gitlab.cern.ch/gaudi/Gaudi/-/issues/135
+            if len( node.getChildren() ) == 0 and node.ModeOR:
+
+              raise RuntimeError( "Empty CF sequence in OR mode can cause Gaudi scheduler bug. Please remove " + node.getName() )
+
             # Identify view CF nodes
             if node.getName() in viewNodes.keys():