'Fixes' an issue changing material back to grass

```
materials: [['grass', 'dirt', 'grass_dirt'], 'brick', 'dirt', 'obsidian', 'crate'],
```

Doesn't allow you to change back to grass, as it's an inner array.
I've just put in something to check that first inner array, can work on a better solution.

Is a for loop to check if each of the array values have inner arrays, the best way?