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: f68c6b3b1dcd5d00a2560c384475aaef3bc99487@9412 af82e41b-90c4-0310-8c96-b1721e28e2e2

dafrito/trac-mirror,dafrito/trac-mirror,moreati/trac-gitsvn,moreati/trac-gitsvn,moreati/trac-gitsvn,dafrito/trac-mirror,dafrito/trac-mirror,exocad/exotrac,exocad/exotrac,exocad/exotrac,exocad/exotrac,moreati/trac-gitsvn