Read sequence worker: adding a file to empty file list is confusing

"Read sequence" worker has a handy button for adding input files (in Property editor). However the button is not "clever" enough to handle a case of empty initial value: it prepends a semicolon to the selected filename. Result is confusing:
1) ugene immediately asks if user wants to split files;
2) running the schema produces unexpected error: "Подзадача

завершена с ошибкой: Файл '' не существует".
Also interesting, the "Add" button is available for sequence reader only, though there 3 more types of readers.

Probably these are 3 separate issues, actually