Nested FormBuilder forms in FileLink get submitted at the same time

[emteknetnz]

May not be relevant depending on whether the FileLink changes back to using the InsertMediaModal.

This related to the currently unmerged PR to add use FormSchema submissions

Clicking a submit button a couple of different forms in a couple of scenarios on selecting a File to link to will also submit the Link Form in the modal. At this point the UploadField won't have a file selected the FileLink will have a FileID of 0.

• Clicking the "Insert File" button that shows below a certain breakpoint (rather than "Insert" button) on the fileSelectForm (i.e. file details form that shows when you select a file from the gallery
• Click the save/publish button on the from that shows after clicking the "details" top-right button of the fileSelectFrom

You can see this behavior by putting a debug breakpoint in FormBuilder.js::handleSubmit()

May actually be a bug with redux-form itself where the forms are listening to submit buttons emitting from entirely different forms.

[emteknetnz]

Duplicate of silverstripe/silverstripe-admin#1662