To reproduce:
1)bring mininet with three switch and 3 hosts,like:
sudo mn --topo=linear,3 --mac --switch ovs --controller=remote,192.168.0.1

2) h1 ping h2 quickly enough before loopremover module to process the topology .
Now The StpStatus of nodeconnectors in network hasn't be fixed.

3) h1 ping h2 will always fail,because the controller doesn't packetout the arp-request packet.
The reason is: At this time, in function dispatchPacket(), inventoryReader.getControllerSwitchConnectors().get(nodeId) is not null;
inventoryReader.getSwitchNodeConnectors().get(nodeId) also is not null,but has no
member in the list.

In the other hand, if the network topology changed which will change the StpStatus of the nodeconnectors ,arphandler module inventoryReader has no way to process this situation.