How to reproduce

• connect to cms
• open resource explorer
• select a directory
• add a file
• do not click on the button to browse you disk

Actual behavior

• a pop-up appear and display a downloading progressing bar

Expected behavior

• no pop-up with progressing bar because there is no file to download!
• a message should be displayed to inform the user to select a file. the user can click on cancel if he does not want to add a file.