This is part of the purpose of version control systems, like git.
When someone makes a new feature, or changes any code at all in fact, they have to commit it to the project. It's a bit like editing here on Stack Exchange: when you edit your post, an item is created in the post's history showing the changes.
If someone sabotages your post (or in this case, project), then you can simply rollback the changes, setting your project back to the state it was in before the change.
The other method is of course backups. If for some reason this disgruntled individual deletes the entire project, backups are your recourse. Taking regular backups means you have a record, kept separately from the project, of the stages of development. You can then simply restore a damaged or deleted project from these backups.