Unable to add additional projects to a group (as project administrator)

I am unable to add more projects to an existing group for which I am a Project Administrator. (Shouldn't this be called Group Administrator?)

1. Create admin user, log in as admin
2. Add m2 project: http://svn.apache.org/repos/asf/tiles/framework/trunk/pom.xml
2a. (this creates the Tiles 2 group, org.apache.tiles)
3. Create user1 account
4. Assign 'Project Administrator - Tiles 2' role to user1
5. log out as admin
6. log in as user1
7. Visit the Tiles 2 project summary page
8. Project Group Actions -> Add M2 Project -> Add
9. Attempt to add http://svn.apache.org/repos/asf/tiles/examples/trunk/tiles-showcase/pom.xml

Result: blank page

Log file from steps 7-9 above is attached.