This bug appears when I set up drag and drop using gridDnD between two grids and the target grid has no rows and has an idPrefix defined.

The problem is the empty row thats created if the drop grid has no rows, the row is created with the id 'jqg_empty_row' and the idPrefix is appended to it when created. And when you try to remove the row up on drop it doesn't exist with id 'jqg_empty_row' due to the idPrefix, so the empty row doesn't get removed.