Return empty dict for MultiParameter without args.

src/jflow/workflow.py

@@ -235,6 +235,7 @@ class Workflow(threading.Thread):
             value = None
         # Set new parameter
         if parameter.__class__ ==  StrParameter or parameter.__class__ == IntParameter or parameter.__class__ == FloatParameter or parameter.__class__ == BoolParameter or parameter.__class__ == DateParameter:
+            if value == "" : value = None # from GUI
             new_param = ParameterFactory.factory( parameter.name, parameter.help, default=value, type=parameter.type, choices=parameter.choices, 
                                                   required=parameter.required, flag=parameter.flag, group=parameter.group, 
                                                   display_name=parameter.display_name )
@@ -250,7 +251,7 @@ class Workflow(threading.Thread):
                                        group=parameter.group, display_name=parameter.display_name, size_limit=parameter.size_limit )
         elif parameter.__class__ == InputFile:
             if value == "" : value = None # from GUI
-            new_param = InputFile( parameter.name, parameter.help, file_format=parameter.file_format, default=parameter.prepare_input_file(value), 
+            new_param = InputFile( parameter.name, parameter.help, file_format=parameter.file_format, default=parameter.prepare_input_file(value),
                                    type=parameter.type, choices=parameter.choices, required=parameter.required, flag=parameter.flag, 
                                    group=parameter.group, display_name=parameter.display_name )
         else:
@@ -266,12 +267,13 @@ class Workflow(threading.Thread):
             if param.__class__ == MultiParameter:
                 new_param = MultiParameter(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
-                sub_args = {}
-                for sarg in args[param.name]:
-                    sub_args[sarg[0]] = sarg[1]
-                for sub_param in param.sub_parameters:
-                    new_sub_parameter = self._prepare_parameter(sub_args, sub_param, "flag")
-                    new_param[new_sub_parameter.name] = new_sub_parameter
+                if args[param.name]:
+                    sub_args = {}
+                    for sarg in args[param.name]:
+                        sub_args[sarg[0]] = sarg[1]
+                    for sub_param in param.sub_parameters:
+                        new_sub_parameter = self._prepare_parameter(sub_args, sub_param, "flag")
+                        new_param[new_sub_parameter.name] = new_sub_parameter
             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