Fixnig the null pointer isssue

components/policy-mgt/org.wso2.carbon.policy.mgt.core/src/main/java/org/wso2/carbon/policy/mgt/core/mgt/impl/MonitoringManagerImpl.java

@@ -229,7 +229,7 @@ public class MonitoringManagerImpl implements MonitoringManager {
         //int tenantId = PolicyManagerUtil.getTenantId();
         Map<Integer, Device> deviceIds = new HashMap<>();
         List<ComplianceData> complianceDatas = new ArrayList<>();
-        HashMap<Integer, Integer> devicePolicyIdMap = null;
+        HashMap<Integer, Integer> devicePolicyIdMap = new HashMap<>();
 
         try {
             PolicyManagementDAOFactory.openConnection();