[imp] "add ... to My Address Book" button on message composition screen behavior change

[Liam Hoekenga]

In IMP 4.0.x and 4.1.x, if you pressed the "add ... to My Address  
Book" button..
- the first time, it would add the address to your address book
- all subsequent times, it would say "Already Exists"

In IMP 4.2, it looks you can press that "add ... to My Address Book"  
button as many times as you like, and it will continue add the same  
address over and over again.

Was this an intentional change?

Liam