ONOS-1802: Added a null check for the returned term

Change-Id: Iacdd8d8f6ef15560bc81162dfefde431271b1204
diff --git a/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java b/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java
index 25f3347..8852c49 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java
@@ -859,7 +859,7 @@
             log.debug("Temporarily requesting role for {} to remove", deviceId);
             mastershipService.requestRoleFor(deviceId);
             MastershipTerm term = termService.getMastershipTerm(deviceId);
-            if (myId.equals(term.master())) {
+            if (term != null && myId.equals(term.master())) {
                 master = myId;
             }
         }