Hello! Thanks for writing in. Hoping to figure this out for you!
So, the first thing you could do is add ?_historyOffset=10 to the end of your URL which will allow you to "travel back in time" 10 steps. You can increase the number to go further back in time if you still don't see any app data. The idea here is to go back to the most recent working version before the chart so you don't have to redo as much work (i.e. going back 10000 steps would likely work, but it could be many, many changes behind).
***WARNING!*** If you make any changes to the canvas when traveling back in time, that past version will become your present version and it messes with the history, so be careful not to touch anything! Once you find a version that isn't crashing and you'd like to make that your present version, then you can make an edit to the canvas (move a component, add a component, etc) to persist that view.
The other thing you could do is download the JSON and make whatever change you wanted (deleting the chart component for example) and then import the new JSON and go from there. If either of these suggestions gives you any trouble, please let us know! And, if you can share any console errors in the future that would also be great! 