fixes for simple-websocket@4

Author: feross

lib/client/websocket-tracker.js

@@ -128,8 +128,11 @@ WebSocketTracker.prototype._onSocketData = function (data) {
   var self = this
   if (self.destroyed) return
 
-  if (!(typeof data === 'object' && data !== null)) {
-    return self.client.emit('warning', new Error('Invalid tracker response'))
+  try {
+    data = JSON.parse(data)
+  } catch (err) {
+    self.client.emit('warning', new Error('Invalid tracker response'))
+    return
   }
 
   if (data.info_hash !== self.client._infoHashBinary) {