Workbench: Added strlen validation to email

Fixed issue where validation passed if email was `''`, causing composer to throw:

```
[Composer\Json\JsonValidationException]
"./composer.json" does not match the expected JSON schema:
 - authors[0].email : Invalid email
```

Now testing for strlen(...)==0 as well
We don't need the extra brackets here, and `===` can be used here rather than `==` too.