Fix issues with bonus xp

[thortol]

Description

Resolves #1168, #1170.

Some issues with the code and fixes the bug where autograded assignments do not have bonus xp awarded. The bug is fixed by updating bonus xp when grading is published.

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update
• [ ] Code quality improvements

Checklist

• [x] I have tested this code
• [ ] I have updated the documentation

[coveralls]

coverage: 94.372%. remained the same when pulling 429aad4867e12a221d132d8ab56a8d33450806b2 on thortol:fix-issues-with-bonus-xp into c0d95e9df86f513b181d8604da37245e6cba8cc3 on source-academy:master.