Removed double sockets.

src/snek/static/app.js

@@ -247,6 +247,8 @@ class Socket extends EventHandler {
         console.info("Connection lost. Reconnecting.");
         this.isConnected = false;
         this.isConnecting = false;
+        this.ws.close();
+        this.ws = null;
         this.ensureConnection().then(() => {
             console.info("Reconnected.");
         });