Added POLICY_REVOKE operation upon deletion of the last policy

components/policy-mgt/org.wso2.carbon.policy.mgt.core/src/main/java/org/wso2/carbon/policy/mgt/core/enforcement/PolicyEnforcementDelegatorImpl.java

@@ -68,12 +68,14 @@ public class PolicyEnforcementDelegatorImpl implements PolicyEnforcementDelegato
             identifier.setType(device.getType());
 
             Policy policy = this.getEffectivePolicy(identifier);
-
-            if (policy != null) {
             List<DeviceIdentifier> deviceIdentifiers = new ArrayList<>();
             deviceIdentifiers.add(identifier);
+            if (policy != null) {
                 this.addPolicyRevokeOperation(deviceIdentifiers);
                 this.addPolicyOperation(deviceIdentifiers, policy);
+            } else {
+                //This means all the applicable policies have been removed from device. Hence calling a policy revoke.
+                this.addPolicyRevokeOperation(deviceIdentifiers);
             }
         }
     }