Ok I've found the issue, it's because I was setting menuOptions[i] to be the new top level action when compiling the menu. This means if we did a sub-menu action in between two top level actions (like magic) when the next top level action is added, i has increased by more than 1 and there will be 0s added in between. For some reason this never threw an error previously. I'm really not sure why it didn't! This probably also explains why a similar error appeared for another user in HTML5. Thanks for the report, I'll upload a fix for this now.