Ah! indeed "clean" shows the error and if you "save", tizen will generate a new ID and fill the properties for you.
For a first version it's ok, but the problem is that when you want to update the game you put in the store, you will need the same package ID.
Otherwise the store system doesn't allows you to upload the binary.
You'll have to either copy/paste the ID back into the config.xml or delete/create the app you uploaded on the store.
I think construct2 should generate this ID. Maybe by simply hashing the project ID or just use java type package if possible.