Avoid lout puking when there is an invalid Joi declaration.

I can generate a 500 with this potentially incorrect Joi declaration (I don't know if this is valid):

Invalid Declaration:
````
var schema = {
    a: Joi.string(),
    b: Joi.array().includes({
            x: Joi.string()
        }
    )
};
```
Correct declaration:
```
var schema = {
    a: Joi.string(),
    b: Joi.array().includes(
        Joi.object({
            x: Joi.string()
        })
    )
};
```
Lout should not 500 in this case but instead should show an error message.