I have done a change, and now the open file crash has gone (b85d5dd9b1a0).

We need to verify how is it possible produce the corrupted file and verify if this was a corner case.

Nice, thanks for the swift fix! I will test this as soon as I can get a build that includes the fix.
The corrupt file was produced by saving while Blender was in the state of waiting for the confirmation or cancellation of the drawing of the ellipse. I mistook this state for a hang, because I had never worked with the tool before and chose it by mistake.
So in order to reproduce, first you need to save a new file (the 2D animation preset works fine). Try to choose the ellipse tool, draw an ellipse, possibly change it a few times, then try to choose the pencil tool again (nothing happens) and then directly try to close the Blender window. The popup offering to save the file should appear and you need to confirm. It doesn't work if you have not saved the file before because the file chooser will be unresponsive in that state.\
What in my opinion should happen is that the drawing of the ellipse should be automatically confirmed when you try switching tools. That's what most other drawing programs do that allow you to draw temporarily adjustable shapes. As a user I don't like to be locked into some state and I can always undo changes I don't like.

I can confirm that the current version (69f50e6ea98) no longer crashes. I have produced a file in that newer version using the process described in my previous comment. It also results in a crash when opened in a version before the fix, so I assume that file is equally corrupted.

If you can open the file with the fix, the corruption is fixed (the read process review the error and fix it automatically). THe reason of the corruption is more related to modal operators.