fix nil pointer dereference in yggdrasil.Conn.search

src/yggdrasil/conn.go

@@ -115,13 +115,13 @@ func (c *Conn) search() error {
 				default:
 					if sinfo != nil {
 						// Finish initializing the session
-						sinfo.setConn(nil, c)
-					}
 						c.session = sinfo
+						c.session.setConn(nil, c)
 						c.nodeID = crypto.GetNodeID(&c.session.theirPermPub)
 						for i := range c.nodeMask {
 							c.nodeMask[i] = 0xFF
 						}
+					}
 					err = e
 					close(done)
 				}