Fix 'CREATE' button when uploading large files

The CREATE button in the CREATE tab of the create dialog opened when clicking on the + icon should be disabled as long as the file is uploading.

How to reproduce:

1. navigate to a workspace or folder
2. click on the + icon and select e.g. PICTURE document type
3. (throttle the network speed in the browser dev tools to a very slow speed)
4. click on the Upload main file link in the CREATE tab and select a large image

Expected result: the CREATE button is disabled until the file is uploaded
Actual result: the CREATE button is immediately active even if the file is not completely uploaded