code simplification

the return made in try and in except was the same. Take it of from both and put
it after.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@31540 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/Image.py

@@ -345,7 +345,6 @@ class Image(File, OFSImage):
                 resolution=resolution, frame=frame, image_size=image_size)
       try:
         mime, image = self.getConversion(**kw)
-        return mime, image.data
       except KeyError:
         mime, image = self._makeDisplayPhoto(**kw)
         self.setConversion(image, mime, **kw)