Data model binding with `dataType` but not `field` renders empty component

### Description of the bug

https://digdir.slack.com/archives/C0760NPT2BE/p1749198260947279


This should show an error instead, noting that a data model binding is required.

### Steps To Reproduce

1. Add a data model binding (the newer object type) without a `field`, to an `Input` component
2. Observe the empty render

### Additional Information

_No response_

Start by reproducing the empty render in an Input component using a newer object-type data model binding with no field, then trace the Input component's data model binding handling. Done means the invalid binding renders an error stating that a data model binding is required, with a regression test covering this case.

Written by the indexing model from the issue text.