Fix focus being lost after adding a new input map entry in the editor

[Calinou]

This allows adding multiple actions in a row by pressing Enter after each action, without needing to click the field again every time.

• This closes "Add New Action" text input loses focus upon adding a new input action #101307.

Preview

input_map_add_action.mp4

[akien-mga]

Seems fine, though we were discussing possibly defaulting that property to true to preserve compatibility with 4.3.

But for now we can merge this fix.

[akien-mga]

Thanks!