I don't suppose you have a savegame where this happens consistently? The error is reported in a line with multiple function calls and it doesn't say which function of what went wrong.
Also did you use world builder at some point?
No, the error is not consistent or reproducable. Reloading a savegame a few turns before the error and playing on did not produce the same error again.
Yes, I did use WB in that game, e.g. to move some bonus resources to a different place and to add 3 minor rivers (Delaware, James River and Potomac).