Check null of pending operations before updating status

components/mobile-plugins/android-plugin/org.wso2.carbon.device.mgt.mobile.android.api/src/main/java/org/wso2/carbon/mdm/services/android/util/AndroidDeviceUtils.java

@@ -582,10 +582,12 @@ public class AndroidDeviceUtils {
             throws DeviceManagementException {
         try {
             List<? extends Operation> pendingOperations = getPendingOperations(deviceIdentifier);
+            if (pendingOperations != null && !pendingOperations.isEmpty()) {
                 for (Operation operation : pendingOperations) {
                     operation.setStatus(Operation.Status.ERROR);
                     AndroidAPIUtils.getDeviceManagementService().updateOperation(deviceIdentifier, operation);
                 }
+            }
         } catch (OperationManagementException e) {
             String msg = "Error occurred while retrieving pending operations to update operation statuses of " +
                          "device to be dis-enrolled";