I did not open the save, but I think I recognize this 
By razing that city you probably triggered the event that has rebels being spawned because of their home city being razed. Now the game does that by drafting units from your enemy. If your enemy cannot draft any units it crashes, just as with colony formation. Since they gave all units drafting ability in the announced patch this will probably be resolved with it. Now of course you could give spain the required techs to build infantry - but I doubt you want that

By razing that city you probably triggered the event that has rebels being spawned because of their home city being razed. Now the game does that by drafting units from your enemy. If your enemy cannot draft any units it crashes, just as with colony formation. Since they gave all units drafting ability in the announced patch this will probably be resolved with it. Now of course you could give spain the required techs to build infantry - but I doubt you want that
