Make default value of event_variables None

Change the default value of event_variables to None instead of an empty FunctorCollection().

Phys/FunTuple/python/FunTuple/functions.py

@@ -14,7 +14,6 @@ from PyConf.Algorithms import FunTupleBase_MCParticles
 from PyConf.Algorithms import FunTupleBase_Composites
 from PyConf.Algorithms import FunTupleBase_ChargedBasics
 from .common_util import conduct_checks_and_transform
-from .FunctorCollection import FunctorCollection
 
 
 def _FunTuple_Base(funtuple_func,
@@ -23,10 +22,13 @@ def _FunTuple_Base(funtuple_func,
                    fields,
                    variables,
                    inputs,
-                   event_variables=FunctorCollection(),
-                   loki_preamble=[],
+                   event_variables=None,
+                   loki_preamble=None,
                    run_full_counter_mode=True,
                    **kwargs):
+    if not loki_preamble:
+        loki_preamble = []
+
     #conduct some type checks and transform to output_args that can be used to set the attributes of FunTupleBase_Particles class
     output_args = conduct_checks_and_transform(name, tuple_name, fields,
                                                variables, loki_preamble)
@@ -36,7 +38,10 @@ def _FunTuple_Base(funtuple_func,
     loki_functor_field_names = output_args[3]
     thor_functors = output_args[4]
     thor_functor_field_names = output_args[5]
-    thor_functor_dict_event_info = event_variables.get_thor_functors()
+    thor_functor_dict_event_info = {}
+    if event_variables:
+        thor_functor_dict_event_info = event_variables.get_thor_functors()
+
     return funtuple_func(
         name=name,
         tuple_name=tuple_name,