I tried creating a poem with no additional poets and got the following error:

```
***UNHANDLED EXCEPTION:  TypeError: Cannot call method 'push' of undefined
    at module.exports.create (/home/david/projects/poemlab/routes/poem.js:50:19)
```

So, it looks like when no poets are added that value will be undefined, as expected, and probably when exactly one poet is added it is a singular value (a string) rather than an array and that's what that other error was about.