remove getting of descriptor. location isn't defined here so it blows up.…

remove getting of descriptor. location isn't defined here so it blows up. Anyhow, the descriptor is being passed into the function, so we don't need to fetch...

cms/djangoapps/contentstore/views.py

@@ -534,7 +534,7 @@ def get_preview_module(request, preview_id, descriptor):
     preview_id (str): An identifier specifying which preview this module is used for
     location: A Location
     """
-    descriptor = modulestore().get_item(location)
+    
     return load_preview_module(request, preview_id, descriptor)