InteractionWorkflow.py: fix isInfoSupported.

product/ERP5Workflow/Document/InteractionWorkflow.py

@@ -118,16 +118,10 @@ class InteractionWorkflow(IdAsReferenceMixin("", "prefix"), Workflow):
     '''
     Returns a true value if the given info name is supported.
     '''
-    for x in self.objectValues(portal_type='Variable'):
-      if x.getReference() == name:
-        vdef = x
-        break
-
-    if vdef is not None:
-      if vdef.getPortalType() == 'Variable':
-        return 1
-      return 0
+    vdef = self.getVariableValueList().get(name, None)
+    if vdef is None:
         return 0
+    return 1
 
   security.declarePrivate('getInfoFor')
   def getInfoFor(self, ob, name, default):