How to reproduce

• connect to cms with a user that has write rights to only one directory
• open resources explorer
• select a file from the directory where this user has rights
• drag it to a directory where this user has no write rights and drop it.

Actual behavior

• an error 500

Expected behavior

• This actions is not possible, a forbidden icon is displayed instead of the +
• OR an explanation message is displayed instead of the error 500