[Bugfix] 修复资产没有管理用户时获取connectivity字段失败的bug

apps/assets/models/asset.py

@@ -250,6 +250,8 @@ class Asset(OrgModelMixin):
 
     @property
     def connectivity(self):
+        if not self.admin_user:
+            return self.UNKNOWN
         return self.admin_user.get_connectivity_of(self)
 
     @connectivity.setter