added null check

drip-api/src/main/java/nl/uva/sne/drip/api/service/ConfigurationService.java

@@ -89,6 +89,9 @@ public class ConfigurationService {
     @PostAuthorize("(returnObject.owner == authentication.name) or (hasRole('ROLE_ADMIN'))")
     public ConfigurationRepresentation delete(String id) {
         ConfigurationRepresentation tr = dao.findOne(id);
+        if(tr == null){
+            throw new NotFoundException();
+        }
         dao.delete(tr);
         return tr;
     }

drip-api/src/main/java/nl/uva/sne/drip/api/service/ProvisionService.java

@@ -250,6 +250,7 @@ public class ProvisionService {
         parameters.add(topology);
 
         Set<String> ids = plan.getLoweLevelPlanIDs();
+        if (ids != null) {
             for (String lowID : ids) {
                 PlanResponse lowPlan = planService.getDao().findOne(lowID);
                 topology = new MessageParameter();
@@ -263,6 +264,7 @@ public class ProvisionService {
                 topology.setAttributes(attributes);
                 parameters.add(topology);
             }
+        }
         return parameters;
     }
 

drip-api/src/main/java/nl/uva/sne/drip/api/v1/rest/ConfigurationController.java

@@ -135,11 +135,16 @@ public class ConfigurationController {
     @RequestMapping(value = "/{id}", method = RequestMethod.DELETE)
     @RolesAllowed({UserService.USER, UserService.ADMIN})
     @StatusCodes({
-        @ResponseCode(code = 200, condition = "Successful delete")
+        @ResponseCode(code = 200, condition = "Successful delete"),
+        @ResponseCode(code = 404, condition = "Object not found")
     })
     public @ResponseBody
     String delete(@PathVariable("id") String id) {
+        try {
             configurationService.delete(id);
+        } catch (NotFoundException ex) {
+            throw ex;
+        }
         return "Deleted : " + id;
     }