Saving unsaved Sketch before signing in with Oauth.

[vivekbopaliya]

Fixes #2334

Changes:
Props to @lindapaiste , he/she figured out how to sort this out while I just stuck two pieces together :)
#2424 (comment)

bandicam.2024-01-13.14-29-38-628.mp4

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123

[lindapaiste]

Awesome! I had not tried out my proposed fix to see if it actually works. You've tried it out and verified it so now it seems good to go 👍. Thanks!