silverstripe-framework: GridFieldPaginator doesn't accept manually entered page numbers

For some reason (currently a mystery to me why), the GridFieldPaginator paginator doesn’t allow you to manually enter a specific page number to go to.

To reproduce:

1. Go to a paginated grid field with 3 or more pages.
2. Important: Ensure that grid field has a name (not a title) with a space in it.
3. Type in the number 3 and press enter.
4. It refreshes the frame and shows just the first page.

This happens even if you start on page 2 or even on page 3. If you clicked the single arrow or double it works as expected (going to the next page or the last page, respectively).

Other symptoms:

• I did notice that in the network transfer, pressing enter did not include the parameter action_gridFieldAlterAction?StateID=gf_2bf77aca (contains the value of Next if you click the arrow and Last if you clicked the double arrow button)
• The ->handleAction() method never gets called when you press enter to submit your new selection.

Edit: Modified instructions to ensure you have a grid field with a name that has a space in it (required to reproduce bug successfully).