Fixed 200 returns when activities are empty and since is a future date

components/device-mgt/org.wso2.carbon.device.mgt.api/src/main/java/org/wso2/carbon/device/mgt/jaxrs/service/impl/ActivityProviderServiceImpl.java

@@ -122,7 +122,7 @@ public class ActivityProviderServiceImpl implements ActivityInfoProviderService
             int count = dmService.getActivityCountUpdatedAfter(timestamp);
             activityList.setCount(count);
             if (activities == null || activities.size() == 0) {
-                if (isIfModifiedSinceSet || isSinceSet) {
+                if (isIfModifiedSinceSet) {
                     return Response.notModified().build();
                 }
             }