added test for hostlocation provider

Change-Id: I37b8efccf2e6c440a416e0d26e519a4d230d7b2a
diff --git a/providers/host/src/main/java/org/onlab/onos/provider/host/impl/HostLocationProvider.java b/providers/host/src/main/java/org/onlab/onos/provider/host/impl/HostLocationProvider.java
index d22106c..d5e739f 100644
--- a/providers/host/src/main/java/org/onlab/onos/provider/host/impl/HostLocationProvider.java
+++ b/providers/host/src/main/java/org/onlab/onos/provider/host/impl/HostLocationProvider.java
@@ -85,6 +85,9 @@
 
         @Override
         public void process(PacketContext context) {
+            if (context == null) {
+                return;
+            }
             Ethernet eth = context.inPacket().parsed();
 
             VlanId vlan = VlanId.vlanId(eth.getVlanID());