Defaults. There's an Underscore function for that (TM)!

For starters, prefer guard clause:
```
if (!project || status !== K.READY_NEW) return;
```
Then do something like this:
```
this.set(_.defaults(this.attributes, {
  owner: project.get('owner'),
  assignedTo: project.get('assignedTo'),
  startDate: ...
  ...
}));
```