ERP5Type.Base: Trivial cleanups for getCreationDate.

- do not use getToolByName.
- do not put two statements on the same line
- merge nested "if" statements around a single code block

product/ERP5Type/Base.py

@@ -3088,19 +3088,19 @@ class Base( CopyContainer,
       Returns the creation date of the document based on workflow information
     """
     # Check if edit_workflow defined
-    portal_workflow = getToolByName(self.getPortalObject(), 'portal_workflow')
+    portal_workflow = self.getPortalObject().portal_workflow
     wf = portal_workflow.getWorkflowById('edit_workflow')
-    wf_list = list(portal_workflow.getWorkflowsFor(self))
-    if wf is not None: wf_list = [wf] + wf_list
+    wf_list = portal_workflow.getWorkflowsFor(self)
+    if wf is not None:
+      wf_list = [wf] + wf_list
     for wf in wf_list:
       try:
         history = wf.getInfoFor(self, 'history', None)
       except KeyError:
         history = None
-      if history is not None:
-        if len(history):
-          # Then get the first line of edit_workflow
-          return history[0].get('time', None)
+      if history is not None and len(history):
+        # Then get the first line of edit_workflow
+        return history[0].get('time', None)
     if getattr(aq_base(self), 'CreationDate', None) is not None:
       return asDate(self.CreationDate())
     return None # JPS-XXX - try to find a way to return a creation date instead of None