Steps to reproduce:

1. Install plugin on jenkins
2. Create a new job or edit an existing job
3. Add a random type parameter (bool, string, whatever)
4. Try to add another parameter - here the menu shows all possible parameter types
5. Add a parameter for this plugin type
6. Try to add another parameter - here the menu is blank, you can't see what you add but by ckicking (blindly) one of the items, the new parameter is added
7. Remove the parameter for this plugin type
8. Try to add another parameter - here the menu shows all possible parameter type