handle handsontable values if empty

src/jflow/workflow.py

@@ -349,6 +349,7 @@ class Workflow(threading.Thread):
             elif param.__class__ == MultiParameterList:
                 new_param = MultiParameterList(param.name, param.help, required=param.required, flag=param.flag, group=param.group, display_name=param.display_name)
                 new_param.sub_parameters = param.sub_parameters
+                if args.has_key(param.name):
                     for idx, sargs in enumerate(args[param.name]):
                         new_multi_param = MultiParameter(param.name + '_' + str(idx), '', required=False, flag=None, group="default", display_name=None)
                         sub_args = {}