Follow-up to r9399, avoid an error when author is None.
Follow-up to r9399, avoid an error when author is None.

{{{
Event provider <tt>TicketModule</tt> failed for filters Opened and closed tickets: <b>AttributeError: 'NoneType' object has
no attribute 'lower'</b>
}}}


git-svn-id: 0d96b0c1a6983ccc08b3732614f4d6bfcf9cbb42@9412 af82e41b-90c4-0310-8c96-b1721e28e2e2

rbaumg/trac,rbaumg/trac,rbaumg/trac,rbaumg/trac