RFMfind SELECT clause requires WHERE clause but should not

It should be possible to SELECT fields returned without requiring a WHERE clause. On Data API backend:
`https://restfm/RESTfm-beta/postcodes/layout/full%20postcodes.json?RFMfind=SELECT%20Pcode`
results in:
```
        "X-RESTfm-FMDataAPI-Status": "400",
        "X-RESTfm-FMDataAPI-Reason": "Find criteria are empty",
```