ONOS-2780 Correcting condition logic.

Change-Id: I6f2b466b7acbdeadcf50ff9efaf651e38c732c9f
diff --git a/core/net/src/main/java/org/onosproject/net/proxyarp/impl/ProxyArpManager.java b/core/net/src/main/java/org/onosproject/net/proxyarp/impl/ProxyArpManager.java
index 1a56d0e..474dd67 100644
--- a/core/net/src/main/java/org/onosproject/net/proxyarp/impl/ProxyArpManager.java
+++ b/core/net/src/main/java/org/onosproject/net/proxyarp/impl/ProxyArpManager.java
@@ -232,7 +232,7 @@
             }
         }
 
-        if (src != null || dst != null) {
+        if (src != null && dst != null) {
             // We know the target host so we can respond
             buildAndSendNdp(targetAddress, dst.mac(), eth, inPort);
             return;