fix(proxy): prevent deleting wrong tunnel in defer cleanup

Add pointer check before delete to handle race where UpdateLocalSNIs
removes our tunnel and a new one is created for the same hostname.

proxy/proxy.go

@@ -608,8 +608,10 @@ func (p *SNIProxy) handleConnection(clientConn net.Conn) {
 		tunnel.count--
 		if tunnel.count == 0 {
 			tunnel.cancel()
+			if p.activeTunnels[hostname] == tunnel {
 				delete(p.activeTunnels, hostname)
 			}
+		}
 		p.activeTunnelsLock.Unlock()
 	}()