[1.0.X] Fixed #10275 -- Corrected the edge case of rendering a LogEntry with a...

[1.0.X] Fixed #10275 -- Corrected the edge case of rendering a LogEntry with a contenttype of None. Thanks to Jarek Zgoda for the report, and Peter Bengtsson for the patch

Merge of r10675 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10676 bcc190cf-cafb-0310-a4f2-bffc1f526a37