What does this error message mean? Error in invocation of storage.set(object items, optional function callback): No matching signatures

I’ve created a Google Chrome extension and originally it was working completely fine. However since Chrome has been updated to Chrome 73 for desktop my extension has failed to work. If I downgrade back to Chrome 72 it works fine. I would like to make my app public soon, which is why I’d like to get this error resolved.

The error alert message that pops up in the browser is referenced below.

Error in invocation of storage.set(object items, optional function callback):No matching signatures.