1. Create a new library
2. Drag'n'drop jablib\build\resources\test\pdfs\minimal.pdf into it
3. See Merge PDF metadata dialog appearing.
4. It first shows a "Grobid" column.
   
5. However, this disappears:
   

Expected result: Dialog closes itself after if there is only one column shown (and the user did not do any manual changes)

This is a follow-up to #13132

It is Expection 1: "No dialog appears, because there is only one "real" source of information"