Add venue / flag venue info allows invalid category selection

[Google Code Exporter]

What steps will reproduce the problem?
1. Start adding a new venue or editing info on existing one
2. Choose top level category (eg. Shops)
3. Submit

What is the expected output? What do you see instead?

User would expect that Shops is saved as venue's category. But since Shops has 
no id, null is sent to server as categoryId. While saving, no error message is 
shown.

CategoryPickerDialog should be changed not to allow selecting categories with 
no id.

Original issue reported on code.google.com by [e-mail] on 5 Aug 2010 at 7:25