Thank you for the bug report! It works on my end, what browser and platform are you on? Does/did it say anything specific?
I also had this bug (first load didn't work, second load ok). Perhaps it's due to the way save data is created, and something is created on the first check that allows the second check to avoid the crash?
On web, attempting to open the editor also results in a crash to desktop, something is calling `notify(msg_str)` with a nil value but no stack trace to follow.