I found three copies of DiscussionDialog.lua, and two of them needed the fix:
* Civilization V.app/Contents/Home/Assets/UI/InGame/LeaderHead/DiscussionDialog.lua was okay
* Civilization V.app/Contents/Home/Assets/DLC/Expansion/UI/InGame/LeaderHead/DiscussionDialog.lua needed the fix in OnButton5()
* Civilization V.app/Contents/Home/Assets/DLC/Expansion2/UI/InGame/LeaderHead/DiscussionDialog.lua needed the fix in OnButton5()
Thanks so much for finding the fix!