timeline: Assume the current date if the "View changes from" field is empty.
timeline: Assume the current date if the "View changes from" field is empty.

Patch by Mikael Relbe. Closes #9271.


git-svn-id: f68c6b3b1dcd5d00a2560c384475aaef3bc99487@9681 af82e41b-90c4-0310-8c96-b1721e28e2e2

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