patch: don't produce a traceback in case of invalid diff content, a warning is enough.
patch: don't produce a traceback in case of invalid diff content, a warning is enough.

Also, skip the patch renderer if it didn't produce any 'diffs'.


git-svn-id: f68c6b3b1dcd5d00a2560c384475aaef3bc99487@9711 af82e41b-90c4-0310-8c96-b1721e28e2e2

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