What is this device protruding from the rear of this 787? While looking at the photos from this question
I noticed a small protrusion from the side of the plane. You can see it in the photo:


and in the diagram from l@aeroalias answer:  



In the diagram it appears to have something to do with the apu or is fire protection system. There's a shaded line running to it. 

What is this object? 



Edit: It does look like an antenna. I found a diagram of 777 antenna placement here, but it doesn't show anything in that area.
As you have already imagined, it's the APU fuel line shroud drain, as visible here:


(Source)

Detail:

  

The fin gives an aerodynamic profile to the drain. The reason this drain exists seems to be:


  Natural fuel leaks from the auxiliary power unit (APU) fueling line
  were supposed to drain harmlessly out the bottom of the structure as
  designed, though rather than do that, the fuel was pooling into the
  APU exhaust cone.


(Source)