Require programming group for streaming the editor

Potentially fixes CODEOCEAN-V2

app/policies/programming_group_policy.rb

@@ -10,6 +10,9 @@ class ProgrammingGroupPolicy < ApplicationPolicy
   end
 
   def stream_sync_editor?
+    # A programming group needs to exist for the user to be able to stream the synchronized editor.
+    return false unless @record
+
     admin? || author_in_programming_group?
   end
 end