filter out "" from active peers in bitswap sessions

We use "" to indicate that the block came from the local node. There's no reason
to record "" as an active peer (doesn't really *hurt* but still...).

License: MIT
Signed-off-by: Steven Allen <steven@stebalien.com>

exchange/bitswap/session.go

@@ -159,7 +159,9 @@ func (s *Session) run(ctx context.Context) {
 		case blk := <-s.incoming:
 			s.tick.Stop()
 
-			s.addActivePeer(blk.from)
+			if blk.from != "" {
+				s.addActivePeer(blk.from)
+			}
 
 			s.receiveBlock(ctx, blk.blk)