I have searched Google and can\'t find anything on this.
I have this code.
In my case, I was need to insert a initial value only to tell to user to select an option, so, I do like the code below:
When I tryed an option with the value != of an empty string (null) the option was substituted by angular, but, when put an option like that (with null value), the select apear with this option.
Sorry by my bad english and I hope that I help in something with this.