Help Me! I can't fix error

What is this error? How can i fix it?

Hi and welcome here
It seems that your file has been messed up because a bone has been deleted.
You can attempt to repair it manually with a text or xml editor.
Also, please add your Version/Bitness/OS

As shown in the picture there are errors in line 16731. I’m opening it with notepad ++. What should I do on this line? Thanks.
(Synfig Studio 1.3.10 | Windows 10)

It depends according the issue, maybe recreate a bone and use it as reference for the other one.
The bone system is a bit broken at the moment, there are some issues reported.
1.2.2 is still considered as the stable version.

Same problem 1.2.2 also exists. I’m going to work more carefully for now. I’m sure, if this error is corrected, the whole synfig studio family will be very happy. Thank you again.

You should deactivate autosave from the preference, then save manually and do backups.
Fixing bones system is WIP, but it is more complex than it seems ^

I have the same issue can you help me to fix it?