frontend: editor: Input Widgets are not configurable in Mini Widget Bar widgets

### Bug description

Attempting to configure an Input Widget in a Mini Widget Bar widget results in the following error:

They work fine to configure in Custom Widget Base widgets, and the Bottom Bar, although per #1585 they can't even be added to the Top Bar.

### Steps to reproduce

1. Open Edit Mode
2. Add a Mini Widgets Bar widget
3. Add an Input Widget to it
4. Try to configure it
5. It doesn't work, and gives an error message

### Primary pain point(s)

Dragging them to a different place to be able to configure them is really clunky and unintuitive - they should be configurable wherever they are in the View.

### Additional context

Possibly related to #1479.

### Prerequisites

- [x] I have checked to make sure that a similar request has not already been filed or fixed.

Reproduce the problem in Edit Mode by placing an Input Widget inside a Mini Widget Bar widget and opening its configuration. Compare that path with configuration in a Custom Widget Base widget or the Bottom Bar; done means Input Widgets can be configured in the Mini Widget Bar without the reported error.

Written by the indexing model from the issue text.