don't try to guess content_type if it's already setup

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@35631 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Tool/ContributionTool.py

@@ -246,7 +246,7 @@ class ContributionTool(BaseTool):
 
     # Then edit the document contents (so that upload can happen)
     document._edit(**kw)
-    if getattr(document, 'guessMimeType', None) is not None:
+    if not document.hasContentType() and getattr(document, 'guessMimeType', None) is not None:
       # For File force to setup the mime_type
       document.guessMimeType(fname=file_name)
     if url: