So I played a strange game where I was trying to basically make the AI opponent make massive armies for me to fight for fun. It took so long I ended up researching the entire tree. The game was set to only allow conquest victories.
Anyway, once I had researched all techs, I cannot end my turn, because it asks for research. (I think maybe there is a way to force the end of a turn, right?)
At any rate, it seems that finishing available research should make it so the game doesn't require you to research to end turn.
(I should add, I mean this should be something that players should be able to do without use of the debug console, since many players don't really know how to do that. Perhaps an option regarding end of turns would be useful to such players)