The build you're using for the main game is out of date. If you download the latest version of OL and add the DLCs to that, the error should go away! I'm glad you enjoyed it so far ^^
Viewing post in Our Life: Beginnings & Always - Cove Wedding Story comments
The save you loaded might be too connected to the error to work even with the new version. If you have a save that's further back in the story you could try that. Or you might unfortunately have to start a new file because the save was broken. You can also try updating the Wedding DLC file itself, if you don't have the most recent version of that. Though, I'm not sure that'd be it. It's likely the save file.