While this fixes the particular issue with xorg-server there are many other source packages in Launchpad all of which would need to have a different binary package name for the guided bug filing instructions to work with 'ubuntu-bug'. I don't think this scales well at all and that apport should be changed to allow bugs to be filed against source packages since Launchpad allows bugs to be filled about source packages.
While this fixes the particular issue with xorg-server there are many other source packages in Launchpad all of which would need to have a different binary package name for the guided bug filing instructions to work with 'ubuntu-bug'. I don't think this scales well at all and that apport should be changed to allow bugs to be filed against source packages since Launchpad allows bugs to be filled about source packages.