Fix bug where left = 0 would be converted to Infinity

Possibly fixes: webtorrent#196

Author: feross

lib/server/parse-websocket.js

@@ -28,7 +28,9 @@ function parseWebSocketRequest (socket, opts, params) {
       params.to_peer_id = common.binaryToHex(params.to_peer_id)
     }
 
-    params.left = Number(params.left) || Infinity
+    params.left = Number(params.left)
+    if (Number.isNaN(params.left)) params.left = Infinity
+
     params.numwant = Math.min(
       Number(params.offers && params.offers.length) || 0, // no default - explicit only
       common.MAX_ANNOUNCE_PEERS