[Idiom] unless it isn't

[Fujibei]

What does "unless it isn't" mean in the following quote from the New York Times?
I understood "unless" means "if ~not" and "unless it isn't" doesn't make sense to me.
[FONT=ＭＳ Ｐゴシック][/FONT]

Onthe emotional fulcrum of New York City apartment-hunting, size and setting areforever in sway. Does a park view trump a guest bedroom? Is a vast kitchenworth settling blocks from a trendy thoroughfare? Usually, a compromise isstruck. Unless it isn't."

​

[FONT=ＭＳ Ｐゴシック][/FONT]

 

[Barb_D]

Unless there is no compromise.

I'm not sure if the writer means that no apartment is found at all, or if an apartment is found that has everything the person wants so there is no need to compromise.

 

[Tarheel]

It seems to me to be saying that people don't usually find everything they want in an apartment. So a compromise is struck. On the other hand, sometimes they do find everything they want.

Fujibei, please take care to space between words. ("Onthe", for example, is two words.)