Open
Description
When trying to expand, the function bot_ai.expand_now calls get_next_expansion which can return a null (will happen late in the game when no expansions are available), however, bot_ai.expand_now does not handle the null returned value.
There should be a check to see if there are any available expansion sites, and if there are not any available, then the null returned value (from get_next_expansion) should have handled without throwing an unexpected exception