webRpc errors

i am using PUN Free.when i use Photonnetwork.webRpc,got a error like
2017-02-18 22:54:47,750 [13] ERROR Photon.SocketServer.PeerBase - exception during handling of data.Peer:T:MasterClientPeer,ConnId:0,ip:127.0.0.1:56326, Data: F3-02-DB-00-02-D1-73-00-0A-50-6C-61-79-65-72-49-6E-66-6F-D0-73-00-04-74-65-73-74,
Exception:System.NullReferenceException: 未将对象引用设置到对象的实例。
在 Photon.LoadBalancing.MasterServer.MasterClientPeer.HandleRpcRequest(OperationRequest operationRequest, SendParameters sendParameters) location d:\dev\photon-socketserver-sdk_cloud\src-server\LoadBalancing\LoadBalancing\MasterServer\MasterClientPeer.cs:line 759
在 Photon.SocketServer.Rpc.Peer.OnOperationRequest(OperationRequest operationRequest, SendParameters sendParameters) location h:\svncontent\photon-socketserver-sdk_cloud\src\Photon.SocketServer\Rpc\Peer.cs:line 109
在 Photon.SocketServer.PeerBase.OnReceive(Byte[] data, SendParameters sendParameters) location h:\svncontent\photon-socketserver-sdk_cloud\src\Photon.SocketServer\PeerBase.cs:line 1243
在 Photon.SocketServer.PeerBase.OnReceiveInternal(Byte[] data, SendParameters sendParameters, Int32 rtt, Int32 rttVariance, Int32 numFailures) location h:\svncontent\photon-socketserver-sdk_cloud\src\Photon.SocketServer\PeerBase.cs:line 988

is this a server error?how to fix ti?