Use project name as logo when the `[header_logo]` / `src` option is blank. Closes #4098.
Use project name as logo when the `[header_logo]` / `src` option is blank. Closes #4098.

git-svn-id: 0d96b0c1a6983ccc08b3732614f4d6bfcf9cbb42@4289 af82e41b-90c4-0310-8c96-b1721e28e2e2

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