If we don't know where to send someone we should send them to the dashboard in Blue
For example: from the /pluginManager
JENKINS-42301 seems to be a duplicate but would be good to check on completion
1. Browse to the plugin manager (/pluginManager/), or credentials
2. Click on "Open Blue Ocean"
3. End up on a 404 at /pluginManager/blue
This occurs for admin links that have a trailing slash (/pluginManager/, /updateCentre/ /credentials/ are some - but this is not an exhaustive list).