Fixed clearing of an export preset's name when deleting the one above it.
Deleting an export preset cleared the name of the item below it. This was
caused by ProjectExportDialog::_edit_preset(-1) which sets the deleted preset's
data to empty values. This on its turn called
ProjectExportDialog::_name_changed() which operates on the new current preset
(the one under the deleted item).
Fixes issue #10842