edx/edx-platform — pull request #5323 by jimabramson (2014-09-22 19:26:01+00:00)
Title: fix 404s when students access group-less threads in cohorted topics

TNL-444

thread access checks were previously checking the presence of the attribute, but sometimes the attribute is present (but null). This change ensures both cases are treated equivalently.

@gwprice @cahrens reqd