修复非众测任务接包人员查看任务报错问题，endpoint校验。

site/src/main/java/com/mooctest/crowd/site/mediator/impl/WebMediatorImpl.java

@@ -887,7 +887,10 @@ public class WebMediatorImpl implements ViewMediator {
                         }).collect(Collectors.toList());
 
                 // 测评机构的endPoint
-                taskVO.setEndPointVO(new EndPointVO(endPoint.getCollaborativeType(), endPoint.getThreePageUrl()));
+                // 判断否存在配置项
+                if(endPoint != null){
+                    taskVO.setEndPointVO(new EndPointVO(endPoint.getCollaborativeType(), endPoint.getThreePageUrl()));
+                }
             }
             taskDetailsDTO.setAcceptedUserList(taskToUserVOS);