Fix saving nbAgg figure after a partial blit

[QuLogic]

PR Summary

While testing out #13971, I realized that it was making an empty blit on click, and that if I hit Save after that, the result would be empty. Also, hitting the Home button would create an image that was a weird mix of the old and new views (whatever the blit looked like.)

Fortunately, this is already fixed in ipympl, so I can just grab the fix from there. This seems to have been broken since forever.

Waiting on the JS re-formatting PR.

PR Checklist

• Has Pytest style unit tests
• [N/A] Code is Flake 8 compliant
• [N/A] New features are documented, with examples if plot related
• [N/A] Documentation is sphinx and numpydoc compliant
• [N/A] Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• [N/A] Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way