Added a check when trying to set application urls and namespace in post_save_page signal.
quickfix for failing redirects with DEBUG=True

This is only a temporary quickfix for a situation where with DEBUG=True all redirects would cause an Exception, because the self.page attribute did not exist.
The real fix would be to find out why this stuff is even being called on redirects.
bumps version to 3.0b4.dev6
Merge pull request #2619 from patrick91/fix_initial_data

Fix DoesNotExist when loading initial_data
Merge branch 'develop' into ticket_1916_develop_merge
Merge branch 'ticket_1916_develop_merge' into ticket_1916_develop
Merge branch 'ticket_1916_develop' into local-develop