Hi Alain,
For some unknown reason, it sometimes happen that the "xxx.ui" project is not appearing in the workspace. Nevertheless, the project has been generatged and exists on your file system, in the directory of your workspace.
So you just have to click on file ->Import...-> General -> Existing project into workspace and then go to the folder of your workspace: everything should work fine now!
Regarding the NullPointerException, it is because you indeed did not select any object ==> the EMF generic generator has a null object as entry point and returns a NullPointerException.
Rgds