{"action":"created","issue":{"url":"https://api.github.com/repos/cjlee112/socraticqs2/issues/104","labels_url":"https://api.github.com/repos/cjlee112/socraticqs2/issues/104/labels{/name}","comments_url":"https://api.github.com/repos/cjlee112/socraticqs2/issues/104/comments","events_url":"https://api.github.com/repos/cjlee112/socraticqs2/issues/104/events","html_url":"https://github.com/cjlee112/socraticqs2/issues/104","id":113108507,"number":104,"title":"Server Error on courselet Concept Tab","user":{"login":"cjlee112","id":59820,"avatar_url":"https://avatars.githubusercontent.com/u/59820?v=3","gravatar_id":"","url":"https://api.github.com/users/cjlee112","html_url":"https://github.com/cjlee112","followers_url":"https://api.github.com/users/cjlee112/followers","following_url":"https://api.github.com/users/cjlee112/following{/other_user}","gists_url":"https://api.github.com/users/cjlee112/gists{/gist_id}","starred_url":"https://api.github.com/users/cjlee112/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/cjlee112/subscriptions","organizations_url":"https://api.github.com/users/cjlee112/orgs","repos_url":"https://api.github.com/users/cjlee112/repos","events_url":"https://api.github.com/users/cjlee112/events{/privacy}","received_events_url":"https://api.github.com/users/cjlee112/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/cjlee112/socraticqs2/labels/bug","name":"bug","color":"fc2929"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":3,"created_at":"2015-10-23T22:07:55Z","updated_at":"2015-10-25T06:24:53Z","closed_at":null,"body":"The following URL generates an 500 Server error:\r\nhttps://www.courselets.org/ct/teach/courses/5/units/29/concepts/"},"comment":{"url":"https://api.github.com/repos/cjlee112/socraticqs2/issues/comments/150896343","html_url":"https://github.com/cjlee112/socraticqs2/issues/104#issuecomment-150896343","issue_url":"https://api.github.com/repos/cjlee112/socraticqs2/issues/104","id":150896343,"user":{"login":"maxsocl","id":877401,"avatar_url":"https://avatars.githubusercontent.com/u/877401?v=3","gravatar_id":"","url":"https://api.github.com/users/maxsocl","html_url":"https://github.com/maxsocl","followers_url":"https://api.github.com/users/maxsocl/followers","following_url":"https://api.github.com/users/maxsocl/following{/other_user}","gists_url":"https://api.github.com/users/maxsocl/gists{/gist_id}","starred_url":"https://api.github.com/users/maxsocl/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/maxsocl/subscriptions","organizations_url":"https://api.github.com/users/maxsocl/orgs","repos_url":"https://api.github.com/users/maxsocl/repos","events_url":"https://api.github.com/users/maxsocl/events{/privacy}","received_events_url":"https://api.github.com/users/maxsocl/received_events","type":"User","site_admin":false},"created_at":"2015-10-25T06:24:53Z","updated_at":"2015-10-25T06:24:53Z","body":"@cjlee112 Problem in `<td><a href=\"{{ actionTarget |get_object_url:concept }}\">` line of concepts.html\r\nEventually Exception occurs in `Concept.get_url` method:\r\n\r\n    return '%s%s/%d/%s' % (basePath, head, objID, tail)\r\n    Exception Type:\tTypeError\r\n    Exception Value:%d format: a number is required, not NoneType\r\n\r\nThis happens due to empty QuierySet `UnitLesson.objects.filter(lesson__concept=self)`:\r\n\r\n    for ul in UnitLesson.objects.filter(lesson__concept=self):\r\n        if objID is None or ul.unit_id == unit_id: # in this unit!\r\n            objID = ul.pk\r\n\r\nSo `objID` is remains `None`.\r\nSo there is no UnitLesson where `lesson.concept` is pointed to `self`."}}