ERP5Workflow: fix getScriptPathList (WorkflowTool) for initial list being None

product/ERP5Workflow/Tool/WorkflowTool.py

@@ -258,6 +258,9 @@ class WorkflowTool(BaseTool, OriginalWorkflowTool):
     return temp_workflow_list
 
   def getScriptPathList(self, workflow, initial_script_name_list):
+    if not initial_script_name_list:
+      return []
+
     script_path_list = []
     if isinstance(initial_script_name_list, str):
       initial_script_name_list = [initial_script_name_list]