Defaults only work if no keys have been defined for a route

If you define metadata defaults like this;

```
/*:
  title: "Default Title"
  description: "Default Description"
```

And then define the metadata for a given page like this;

```
/help:
  title: "Help Title"
```

The expected behavior would be for the default description to be used on `/help`, but instead only a title is used, and there is no description.
